Drop System.Linq from CommunityToolkit.Diagnostics

[Sergio0694]

See dotnet/runtime#82607 (comment)

This PR removes the dependency on System.Linq from CommunityToolkit.Diagnostics. This will help reduce binary size in NAOT builds using any of the Guard APIs, or the ToTypeString() extension directly, especially with default settings.

PR Checklist

• Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• Based off latest main branch of toolkit
• PR doesn't include merge commits (always rebase on top of our main, if needed)
• Tested code with current supported SDKs
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes
• Every new API (including internal ones) has full XML docs
• Code follows all style conventions