Add NonAsyncDisposableTypeAttribute for await using

[meziantou]

NonAwaitableTypeAttribute was suppressing both await and await using recommendations, which made it impossible to opt out of only await using guidance. This change separates those concerns so projects can configure each behavior independently.

What changed

• Added NonAsyncDisposableTypeAttribute in Meziantou.Analyzer.Annotations for await using suppression.
• Updated MA0042/MA0045 await-using analysis to honor only NonAsyncDisposableTypeAttribute.
• Kept NonAwaitableTypeAttribute for awaitability checks (await) only.
• Updated analyzer internals to detect both attributes separately.
• Updated tests in async and non-async MA0042 suites to lock the new behavior.
• Updated documentation for MA0042, MA0045, and annotations README.
• Bumped Meziantou.Analyzer.Annotations version to 1.5.0.

Notes for reviewers

This intentionally changes behavior: existing projects that used NonAwaitableTypeAttribute to suppress await using diagnostics now need to use NonAsyncDisposableTypeAttribute.

Fix #1152