Add RequiresUnsafe trimming analyzer capabilities

[agocke]

This is a debug-only mode that we can use for annotating the framework. No intention of shipping this implementation.

[Copilot]

Pull request overview

Adds a debug-only “RequiresUnsafe” analyzer path (plus code fix + tests) to help annotate the framework, gated behind an MSBuild property and excluded from shipping builds.

Changes:

• Extend the Roslyn analyzer test harness to optionally compile test inputs with allowUnsafe.
• Add a debug-only RequiresUnsafeAnalyzer and a debug-only code fix provider.
• Add diagnostics/resources for the new RequiresUnsafe warnings and introduce a new test suite for them (DEBUG-only).

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/Verifiers/CSharpAnalyzerVerifier`1.cs	Adds an overload to pass allowUnsafe through the verifier into compilation creation.
src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/TestCaseCompilation.cs	Adds allowUnsafe support to the Roslyn compilation options and refactors supported analyzer list creation.
src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/RequiresUnsafeAnalyzerTests.cs	New DEBUG-only tests validating RequiresUnsafe diagnostics and suppression behavior in unsafe { } blocks.
src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/RequiresUnreferencedCodeAnalyzerTests.cs	Removes an unused diagnostic descriptor field.
src/tools/illink/src/ILLink.Shared/SharedStrings.resx	Adds title/message resources for the new RequiresUnsafe diagnostics.
src/tools/illink/src/ILLink.Shared/DiagnosticId.cs	Introduces DEBUG-only diagnostic IDs for RequiresUnsafe and adjusts AOT subcategory mapping.
src/tools/illink/src/ILLink.RoslynAnalyzer/RequiresUnsafeAnalyzer.cs	New DEBUG-only analyzer implementation, enabled via an MSBuild property, with special “unsafe block” suppression.
src/tools/illink/src/ILLink.RoslynAnalyzer/RequiresAnalyzerBase.cs	Refactors scope suppression check to be overridable by derived analyzers.
src/tools/illink/src/ILLink.RoslynAnalyzer/MSBuildPropertyOptionNames.cs	Adds a DEBUG-only MSBuild property name for enabling the new analyzer.
src/tools/illink/src/ILLink.RoslynAnalyzer/DynamicallyAccessedMembersAnalyzer.cs	Includes RequiresUnsafeAnalyzer in the “requires analyzers” set in DEBUG builds.
src/tools/illink/src/ILLink.CodeFix/Resources.resx	Adds a localized title for the RequiresUnsafe code fix.
src/tools/illink/src/ILLink.CodeFix/RequiresUnsafeCodeFixProvider.cs	New DEBUG-only code fix provider: add RequiresUnsafe attribute and optionally wrap a statement in an unsafe block.

[sbomer]

This needs some tests for the code fixer too I think.

[agocke]

Moving to draft as I clean this up

[Copilot]

Pull request overview

Copilot reviewed 20 out of 20 changed files in this pull request and generated 5 comments.

[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated 6 comments.

[agocke]

@sbomer OK, I think this is ready again. The code fixer code is kind of a mess, but it's not totally wrong, and it's working enough for local prototyping. We don't plan to ship it, so it seems fine.

[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated 6 comments.

[sbomer]

A few nits, otherwise LGTM!