[native, Mono.Android] Remove internal/obsolete System.AndroidPlatform methods (#10385)

Fixes: #10381

This PR removes obsolete managed code that references
`System.AndroidPlatform`, which was part of the Xamarin.Android runtime
but was never used in modern .NET. The issue was identified by
@filipnavara and confirmed safe to remove by @jonathanpeppers after
verifying that these APIs don't exist in dotnet/runtime.

## Changes Made

**Removed Methods from AndroidEnvironment.cs:**

- `GetDisplayDPI()` - Previously called by
  `System.Drawing.GraphicsAndroid.FromAndroidSurface()` (already
  marked as obsolete for android31.0)
- `GetDefaultTimeZone()` - Previously called by
  `System.Core!System.AndroidPlatform.GetDefaultTimeZone()`
- `GetDefaultSyncContext()` - Previously called by
  `mscorlib.dll!System.AndroidPlatform.GetDefaultSyncContext()`
- `GetInterfaceAddresses()` - Previously called by
  `System.dll!System.AndroidPlatform.getifaddrs`
- `FreeInterfaceAddresses()` - Previously called by
  `System.dll!System.AndroidPlatform.freeifaddrs`
- `GetDefaultProxy()` - Previously called by
  `System.dll!System.AndroidPlatform.GetDefaultProxy()`

**Additional Cleanup:**

- Removed the `_Proxy` class that was only used by `GetDefaultProxy()`
- Removed unused P/Invoke declarations from `RuntimeNativeMethods.cs`:
  - `_monodroid_timezone_get_default_id()`
  - `_monodroid_getifaddrs()`
  - `_monodroid_freeifaddrs()`

**Native Code Cleanup:**

- Removed P/Invoke method entries from both CLR and Mono P/Invoke
  table generators
- Regenerated P/Invoke tables using `generate-pinvoke-tables.sh`
- Removed unused native C++ implementations:
  - `_monodroid_timezone_get_default_id()` functions (CLR & Mono)
  - Complete `xamarin_getifaddrs.cc` files and header (CLR & Mono -
    2,200+ lines)
  - Updated CMakeLists.txt files to remove build references
- Fixed linker error by removing obsolete symbols from Mono version
  script

## Impact

This is a **breaking change** that removes internal APIs that were
never intended for public use in modern .NET for Android. No external
code should be affected as these were internal implementation details
for obsolete `System.AndroidPlatform` methods.

Co-authored-by: Jonathan Peppers <[email protected]>

Author: Copilot

src/Mono.Android/Android.Runtime/AndroidEnvironment.cs

@@ -228,85 +228,6 @@ static void NotifyTimeZoneChanged ()
 			}
 		}
 
-		// This is invoked by
-		// System.Drawing!System.Drawing.GraphicsAndroid.FromAndroidSurface ()
-		// DO NOT REMOVE
-		//
-		// Exception audit:
-		//
-		//  Verdict
-		//     No need to wrap thrown exceptions in a BCL class
-		//
-		//  Rationale
-		//     No longer called by the indicated caller, however we keep it for backward compatibility.
-		[global::System.Runtime.Versioning.ObsoletedOSPlatform ("android31.0")]
-		static void GetDisplayDPI (out float x_dpi, out float y_dpi)
-		{
-			var wm = Application.Context.GetSystemService (Context.WindowService).JavaCast <IWindowManager> ();
-			var metrics = new DisplayMetrics ();
-#if ANDROID_17
-			wm?.DefaultDisplay?.GetRealMetrics (metrics);
-#else
-			wm.DefaultDisplay.GetMetrics (metrics);
-#endif
-			x_dpi = metrics.Xdpi;
-			y_dpi = metrics.Ydpi;
-		}
-
-		// This is invoked by
-		// System.Core!System.AndroidPlatform.GetDefaultTimeZone ()
-		// DO NOT REMOVE
-		//
-		// Exception audit:
-		//
-		//  Verdict
-		//    No need to wrap thrown exceptions in a BCL class
-		//
-		//  Rationale
-		//    Java code (invoked from our native runtime) will always return the default timezone and no
-		//    exceptions are documented for the Java API.
-		//
-		static string GetDefaultTimeZone ()
-		{
-			IntPtr id = RuntimeNativeMethods._monodroid_timezone_get_default_id ();
-			try {
-				return Marshal.PtrToStringAnsi (id)!;
-			} finally {
-				RuntimeNativeMethods.monodroid_free (id);
-			}
-		}
-
-		// This is invoked by
-		// mscorlib.dll!System.AndroidPlatform.GetDefaultSyncContext()
-		// DO NOT REMOVE
-		static SynchronizationContext? GetDefaultSyncContext ()
-		{
-			var looper = Android.OS.Looper.MainLooper;
-			try {
-				if (Android.OS.Looper.MyLooper() == looper)
-					return Android.App.Application.SynchronizationContext;
-			} catch (System.Exception ex) {
-				Logger.Log (LogLevel.Warn, "MonoAndroid", $"GetDefaultSyncContext caught a Java exception: {ex}");
-			}
-			return null;
-		}
-
-		// These are invoked by
-		// System.dll!System.AndroidPlatform.getifaddrs
-		// DO NOT REMOVE
-		static int GetInterfaceAddresses (out IntPtr ifap)
-		{
-			return RuntimeNativeMethods._monodroid_getifaddrs (out ifap);
-		}
-
-		// These are invoked by
-		// System.dll!System.AndroidPlatform.freeifaddrs
-		// DO NOT REMOVE
-		static void FreeInterfaceAddresses (IntPtr ifap)
-		{
-			RuntimeNativeMethods._monodroid_freeifaddrs (ifap);
-		}
-
 		static void DetectCPUAndArchitecture (out ushort builtForCPU, out ushort runningOnCPU, out bool is64bit)
 		{
 			ushort built_for_cpu = 0;
@@ -319,18 +240,6 @@ static void DetectCPUAndArchitecture (out ushort builtForCPU, out ushort running
 			is64bit = _is64bit != 0;
 		}
 
-		// This is invoked by
-		// System.dll!System.AndroidPlatform.GetDefaultProxy()
-		// DO NOT REMOVE
-		static IWebProxy GetDefaultProxy ()
-		{
-#if ANDROID_14
-			return new _Proxy ();
-#else
-			return null;
-#endif
-		}
-
 		// This is invoked by
 		// System.Net.Http.dll!System.Net.Http.HttpClient.cctor
 		// DO NOT REMOVE
@@ -395,61 +304,5 @@ static Type GetFallbackHttpMessageHandlerType ()
 			return handlerType;
 		}
 
-		class _Proxy : IWebProxy {
-			readonly ProxySelector selector = ProxySelector.Default!;
-
-			// Exception audit:
-			//
-			//  Verdict
-			//    Exception wrapping required
-			//
-			//  Rationale
-			//    Java code may throw URISyntaxException which we map to the managed UriFormatException
-			//
-			static URI CreateJavaUri (Uri destination)
-			{
-				try {
-					return new URI (destination.Scheme, destination.UserInfo, destination.Host, destination.Port, destination.AbsolutePath, destination.Query, destination.Fragment);
-				} catch (Java.Lang.Throwable ex) when (JNIEnv.ShouldWrapJavaException (ex)) {
-					throw new UriFormatException (ex.Message, ex);
-				}
-			}
-
-			public Uri GetProxy (Uri destination)
-			{
-				IList<Java.Net.Proxy> list;
-				using (var uri = CreateJavaUri (destination))
-					list = selector.Select (uri)!;
-				if (list.Count < 1)
-					return destination;
-
-				var proxy = list [0];
-				if (proxy.Equals (Proxy.NoProxy))
-					return destination;
-
-				var address = proxy.Address () as InetSocketAddress;
-				if (address == null) // FIXME
-					return destination;
-
-				return new Uri (FormattableString.Invariant ($"http://{address.HostString}:{address.Port}/"));
-			}
-
-			public bool IsBypassed (Uri host)
-			{
-				IList<Java.Net.Proxy> list;
-				using (var uri = CreateJavaUri (host))
-					list = selector.Select (uri)!;
-
-				if (list.Count < 1)
-					return true;
-
-				return list [0].Equals (Proxy.NoProxy);
-			}
-
-			public ICredentials? Credentials {
-				get;
-				set;
-			}
-		}
 	}
 }

src/Mono.Android/Android.Runtime/RuntimeNativeMethods.cs

@@ -45,14 +45,6 @@ internal unsafe static class RuntimeNativeMethods
 		[DllImport (RuntimeConstants.InternalDllName, CallingConvention = CallingConvention.Cdecl)]
 		internal static extern IntPtr _monodroid_lookup_replacement_method_info (string jniSourceType, string jniMethodName, string jniMethodSignature);
 
-		[DllImport (RuntimeConstants.InternalDllName, CallingConvention = CallingConvention.Cdecl)]
-		internal static extern IntPtr _monodroid_timezone_get_default_id ();
-
-		[DllImport (RuntimeConstants.InternalDllName, CallingConvention = CallingConvention.Cdecl)]
-		internal static extern int _monodroid_getifaddrs (out IntPtr ifap);
-
-		[DllImport (RuntimeConstants.InternalDllName, CallingConvention = CallingConvention.Cdecl)]
-		internal static extern void _monodroid_freeifaddrs (IntPtr ifap);
 
 		[DllImport (RuntimeConstants.InternalDllName, CallingConvention = CallingConvention.Cdecl)]
 		internal static extern void _monodroid_detect_cpu_and_architecture (ref ushort built_for_cpu, ref ushort running_on_cpu, ref byte is64bit);

src/native/clr/host/CMakeLists.txt

@@ -39,7 +39,6 @@ set(XAMARIN_MONODROID_SOURCES
   runtime-environment.cc
   runtime-util.cc
   typemap.cc
-  xamarin_getifaddrs.cc
 )
 
 if(DEBUG_BUILD)

src/native/clr/host/internal-pinvokes-clr.cc

@@ -65,24 +65,3 @@ void monodroid_timing_stop (managed_timing_sequence *sequence, const char *messa
 	Timing::info (sequence, message == nullptr ? DEFAULT_MESSAGE.data () : message);
 	timing->release_sequence (sequence);
 }
-
-void* _monodroid_timezone_get_default_id ()
-{
-	JNIEnv *env			 = OSBridge::ensure_jnienv ();
-	jmethodID getDefault = env->GetStaticMethodID (Host::get_java_class_TimeZone (), "getDefault", "()Ljava/util/TimeZone;");
-	jmethodID getID		 = env->GetMethodID (Host::get_java_class_TimeZone (), "getID",		 "()Ljava/lang/String;");
-	jobject d			 = env->CallStaticObjectMethod (Host::get_java_class_TimeZone (), getDefault);
-	jstring id			 = reinterpret_cast<jstring> (env->CallObjectMethod (d, getID));
-	const char *mutf8	 = env->GetStringUTFChars (id, nullptr);
-	if (mutf8 == nullptr) {
-		log_error (LOG_DEFAULT, "Failed to convert Java TimeZone ID to UTF8 (out of memory?)"sv);
-		env->DeleteLocalRef (id);
-		env->DeleteLocalRef (d);
-		return nullptr;
-	}
-	char *def_id		 = strdup (mutf8);
-	env->ReleaseStringUTFChars (id, mutf8);
-	env->DeleteLocalRef (id);
-	env->DeleteLocalRef (d);
-	return def_id;
-}