Merge rust-bitcoin#3655: Manually backport 3640

8d2267c backport: address: Add `Address::into_unchecked` (Tobin C. Harding)
499dd80 backport: address: Simplify `Address::assume_checked` impl (Tobin C. Harding)

Pull request description:

  Manually backport the 2 patches from rust-bitcoin#3640. I did not investigate why the patches didn't apply cleanly I just grabed the changes from each patch. I did keep the patches separate and retained the commit logs. Holla if there is a better way to do this since we are backporting often these days.

ACKs for top commit:
  MaxFangX:
    ACK [`8d2267c`](rust-bitcoin@8d2267c), confirmed use of `Address::into_unchecked` compiles and passes tests downstream with patch
  apoelstra:
    ACK 8d2267c; successfully ran local tests

Tree-SHA512: 92ae39092d9ced3d1597305328589dbeecd7659b445302b442a715c9af82d5d664c7d75ddd95ab4b39b0908df5c1ea54455f9675d72f33f884bbd8208aa32dbb

Author: apoelstra

bitcoin/src/address/mod.rs

@@ -382,6 +382,9 @@ impl<V: NetworkValidation> Address<V> {
     pub fn as_unchecked(&self) -> &Address<NetworkUnchecked> {
         unsafe { &*(self as *const Address<V> as *const Address<NetworkUnchecked>) }
     }
+
+    /// Marks the network of this address as unchecked.
+    pub fn into_unchecked(self) -> Address<NetworkUnchecked> { Address(self.0, PhantomData) }
 }
 
 /// Methods and functions that can be called only on `Address<NetworkChecked>`.
@@ -773,16 +776,7 @@ impl Address<NetworkUnchecked> {
     /// For details about this mechanism, see section [*Parsing addresses*](Address#parsing-addresses)
     /// on [`Address`].
     #[inline]
-    pub fn assume_checked(self) -> Address {
-        use AddressInner::*;
-
-        let inner = match self.0 {
-            P2pkh { hash, network } => P2pkh { hash, network },
-            P2sh { hash, network } => P2sh { hash, network },
-            Segwit { program, hrp } => Segwit { program, hrp },
-        };
-        Address(inner, PhantomData)
-    }
+    pub fn assume_checked(self) -> Address { Address(self.0, PhantomData) }
 }
 
 impl From<Address> for script::ScriptBuf {