Use ForAttributeWithMetadataName<T> when possible

[Sergio0694]

Closes #424

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

[Nirmal4G]

I'm actually trying to make the multi-targeting work via TargetFrameworks property by using a custom TargetFramework property (like: netstandard2.0-roslyn4.0). It's a work in progress as there's an issue with NuGet not accepting custom frameworks.

Another way is, trying to use Platform property (like: Roslyn v4.0) to specify Roslyn versions. This is the simplest one but it could confuse people. So, trying the former first.

If any of these solutions work, then much of the MSBuild project changes here no longer apply. We could maitain everything in a single project.

[Sergio0694]

I'd really like to avoid messing with custom TFMs. Using a shared project is perfectly fine.