Class property metadata cannot represent public indexer getters #7553

Summary

Class property metadata includes public indexers even though its getter delegate accepts no index arguments. Generated metadata emits ordinary property access for an indexer, which cannot compile; the reflection metadata implementation in PR #7550 invokes it without arguments and throws. Both discovery modes should handle indexers consistently.

Reproduction

Add a test fixture with a public indexer:

public class IndexerTests
{
    public string this[int index] => index.ToString();
    [Test]
    public void Example() { }
}

MetadataGenerationHelper.WritePropertyMetadataArray includes every declared public property, while GetPropertyAccessor emits ((IndexerTests)o).this[] instead of an indexed access. PR #7550 (closing #7522) adds reflection class metadata using p.GetValue(instance) without index arguments. Current main still leaves that reflection property array empty. This follows directly from the source; a dedicated compiler regression is still needed.

Expected and actual

Exclude indexers from class property metadata in both discovery modes; the existing getter API accepts no index arguments. Currently the metadata getter contract cannot represent them.

Environment

Inspected main at 10a0af7; .NET SDK 10.0.403. Source: https://github.com/thomhurst/TUnit/blob/10a0af7272/src/TUnit.Core.SourceGenerator/Utilities/MetadataGenerationHelper.cs#L347 and #L494.

Please add consistent indexer handling and regression coverage. Discovered while reviewing #7550.

Acceptance criteria

• Exclude public indexers from generated and reflection class property metadata while preserving ordinary public instance and static properties.
• Add a generator compiler/snapshot regression for a class with a public indexer.
• Verify metadata and ordinary property getters in both discovery modes, including a generic class, and preserve AOT compatibility.

Triage at main 4891fce71adee5d0d66e19c9fc20a367b9cca1e9: the generator still includes indexers. Complete this follow-up after #7522 so regression coverage exercises the populated reflection metadata introduced by #7550.