[3.0] Streamline native builds (and build native libs for 3.0)

[Perksey]

Adds SDL native builds and a much more streamlined native workflow.

More info in the for-contributors doc.

[github-actions]

File	Coverage
All files	3%	✅

Minimum allowed coverage is 0%

Generated by 🐒 cobertura-action against 3beeabc

[github-actions]

All native library builds modified in this PR shall attempt to be built by CI.

[github-actions]

Some of the native library builds modified in this PR were not referenced in the PR description. Please ensure that the PR description contains /build-native SDL. These libraries won't be rebuilt without this being specified. If you believe this is in error, then please write a comment explaining why and ignore this suggestion. This comment will be automatically updated if rectified.

[Perksey]

Removed that from the PR description as the Build/Test jobs, which are required to merge, don't run on the bot commits.

[Perksey]

I don't know how to change it so it doesn't do that either, ideally we'd have paths-filter use the last dotnet-bot commit as the base for the compare (or obviously the target branch as it is today if we haven't done that yet) as it'd lessen the problem by making it so the last commit isn't always a bot commit. We'd have to fork the action, and I don't feel like doing that right now.