Fixed Guard APIs CS8777 warnings

[Sergio0694]

Follow up for #3167.

This feature adds the [DoesNotReturnAttribute] to internal throw methods, including a local copy for the .NET Standard 2.0 target. This fixes the nullability warnings, which were causing the build to fail.

PR Type

What kind of change does this PR introduce?

• Bugfix

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Pull Request has been submitted to the documentation repository instructions. Link:
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• 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

Other information

[ghost]

Thanks Sergio0694 for opening a Pull Request! The reviewers will test the PR and highlight if there is any conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌

[michael-hawker]

I couldn't repro the original issue on my 2004 VS 16.5.5, forgot to try on newer VS. but LGTM

[michael-hawker]

@Sergio0694 I've noticed a lot of your PRs have a ton of merge tracking commits listed, it almost seems like your master may be out of sync or something with the main fork?

[Sergio0694]

@michael-hawker I had actually merged from upstream/master into my master right before branching off to make this PR, I thought that would've gotten rid of those merge commits 😕

Looks like they're all still listed there instead, is there something I should do to fix that?
I mean, my master is in sync with the toolkit's master now 🤔

Sorry for the clutter!

[michael-hawker]

@Sergio0694 I'm not sure outside of force-pushing the master from the toolkit over your master and rebasing/fixing branches?

[Sergio0694]

Hey @michael-hawker, sorry I missed this notification!
I'll try that force push, thanks for the suggestion! 😊