Remove RequiresUnsafeAnalyzer

[jjonescz]

See #127761 (comment).
Related to #125800 and dotnet/roslyn#81207.

[dotnet-policy-service]

Tagging subscribers to this area: @agocke, @dotnet/illink
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR removes the experimental RequiresUnsafe / UnsafeMethodMissingRequiresUnsafe analyzers and related code fixes from the ILLink Roslyn analyzer toolset, along with their tests and resource strings. This aligns ILLink’s analyzer/test infrastructure with the Roslyn direction that RequiresUnsafeAttribute should not be authored in source (favoring the unsafe modifier instead).

Changes:

• Remove RequiresUnsafeAnalyzer and UnsafeMethodMissingRequiresUnsafeAnalyzer, plus their associated DiagnosticId entries and shared resource strings.
• Remove corresponding code fix providers (RequiresUnsafeCodeFixProvider and UnsafeMethodMissingRequiresUnsafeCodeFixProvider) and all related analyzer/code-fix tests.
• Stop wiring the removed analyzer into analyzer/test composition and remove the EnableUnsafeAnalyzer compiler-visible property from the ILLink analyzer props.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/UnsafeMethodMissingRequiresUnsafeTests.cs	Removes tests for the “missing RequiresUnsafe” analyzer and its code fix.
src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/TestCaseCompilation.cs	Stops adding RequiresUnsafeAnalyzer to the supported analyzer set in tests.
src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/RequiresUnsafeCodeFixTests.cs	Removes code fix tests that manipulate RequiresUnsafeAttribute usage.
src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/RequiresUnsafeAnalyzerTests.cs	Removes analyzer tests for RequiresUnsafe diagnostics.
src/tools/illink/src/ILLink.Shared/SharedStrings.resx	Removes shared strings for RequiresUnsafe-related diagnostics/titles/messages.
src/tools/illink/src/ILLink.Shared/DiagnosticId.cs	Removes DEBUG-only RequiresUnsafe diagnostic IDs and subcategory mapping.
src/tools/illink/src/ILLink.RoslynAnalyzer/UnsafeMethodMissingRequiresUnsafeAnalyzer.cs	Deletes the analyzer that suggested adding RequiresUnsafeAttribute for pointer-signature members.
src/tools/illink/src/ILLink.RoslynAnalyzer/RequiresUnsafeAnalyzer.cs	Deletes the analyzer producing RequiresUnsafe diagnostics.
src/tools/illink/src/ILLink.RoslynAnalyzer/MSBuildPropertyOptionNames.cs	Removes the DEBUG-only EnableUnsafeAnalyzer property constant.
src/tools/illink/src/ILLink.RoslynAnalyzer/DynamicallyAccessedMembersAnalyzer.cs	Stops registering the removed RequiresUnsafe analyzer in the “requires analyzers” set.
src/tools/illink/src/ILLink.RoslynAnalyzer/build/Microsoft.NET.ILLink.Analyzers.props	Removes EnableUnsafeAnalyzer from compiler-visible properties list.
src/tools/illink/src/ILLink.CodeFix/UnsafeMethodMissingRequiresUnsafeCodeFixProvider.cs	Deletes the code fix provider that adds RequiresUnsafeAttribute to pointer-signature members.
src/tools/illink/src/ILLink.CodeFix/Resources.resx	Removes code-fix resource strings tied to the deleted code fixes.
src/tools/illink/src/ILLink.CodeFix/RequiresUnsafeCodeFixProvider.cs	Deletes the code fix provider for RequiresUnsafe diagnostics (“add attribute” / “wrap in unsafe block”).