Add field support to DynamicDataAttribute

[Copilot]

This PR adds support for public static fields as data sources in DynamicDataAttribute, addressing a key performance improvement request for test data management.

Problem

Previously, DynamicDataAttribute only supported properties and methods as data sources. This meant that even for constant test data, new objects were created on each access due to property getters or method calls, despite being static:

// Property - creates new array on each access
public static IEnumerable<object[]> TestData => new[]
{
    new object[] { 25, 250 },
    new object[] { 42, 420 },
    new object[] { 164, 1640 }
};

// Method - also creates new array on each call  
public static IEnumerable<object[]> GetTestData() => new[]
{
    new object[] { 25, 250 },
    new object[] { 42, 420 },
    new object[] { 164, 1640 }
};

Solution

Added comprehensive support for static fields as data sources, allowing truly constant test data:

// Field - created once, reused efficiently
public static int[][] TestData = new[]
{
    new[] { 25, 250 },
    new[] { 42, 420 },
    new[] { 164, 1640 }
};

[TestMethod]
[DynamicData(nameof(TestData), DynamicDataSourceType.Field)]
public void TestWithExplicitField(int input, int expected) { /* ... */ }

[TestMethod]
[DynamicData(nameof(TestData))] // Auto-detect also works
public void TestWithAutoDetect(int input, int expected) { /* ... */ }

Key Features

• Explicit field specification: DynamicDataSourceType.Field for direct field targeting
• Auto-detection support: Fields are discovered automatically after properties and methods
• External class support: Works with fields in other classes via declaring type parameter
• Inheritance support: Fields from base classes are properly resolved
• Full integration: Complete support in analyzer, source generation, and runtime
• Comprehensive validation: Proper error messages for non-static fields and type mismatches

Implementation Details

• Extended DynamicDataSourceType enum with Field = 3 option
• Added field detection and data extraction methods in DynamicDataOperations
• Updated auto-detect logic with priority: Property → Method → Field
• Enhanced analyzer to validate field usage and provide appropriate diagnostics
• Updated source generation to handle field symbols correctly
• Added comprehensive test coverage for all field scenarios

Backward Compatibility

This change is fully backward compatible - all existing code continues to work exactly as before. The new field support is purely additive functionality.

Fixes #5321.

Warning

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