Fix: Unsupported maccatalyst attribute is getting applied to child attributes but not accounted parent child attributes merge

[buyaa-n]

When an API supported on IOS it also supported by maccatalyst as they are related. To remove implicit maccatalyst support one need to add [UnsupportedOSPlatform (""maccatalyst"")] to the [SupportedOSPlatform (""ios"")]

The [UnsupportedOSPlatform (""maccatalyst"")] applied to the immediate (child) attributes list and removed the implicit maccatalyst support but when child attributes are merged to the parent attributes list this is not accounted and merged list will keep the implicit maccatalyst support. The PR fixes this bug

Fixes #7633

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.84%. Comparing base (d802d62) to head (187216b).
Report is 21 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##             main    #7644     +/-   ##
=========================================
  Coverage   96.83%   96.84%             
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  Files        1215     1220      +5     
  Lines      307561   308792   +1231     
  Branches     9513     9554     +41     
=========================================
+ Hits       297842   299050   +1208     
- Misses       7380     7396     +16     
- Partials     2339     2346      +7     

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[rolfbjarne]

This regresses the following sample/unit test: rolfbjarne@84ddcbc, it shows:

Diagnostics:
// /0/Test0.cs(22,20): warning CA1416: This call site is reachable on: 'ios', 'macOS/OSX', 'tvos'. 'NativeObjectExtensions.GetHandle(INativeObject)' is only supported on: 'maccatalyst'.

[buyaa-n]

This regresses the following sample/unit test: rolfbjarne@84ddcbc, it shows:

Diagnostics:
// /0/Test0.cs(22,20): warning CA1416: This call site is reachable on: 'ios', 'macOS/OSX', 'tvos'. 'NativeObjectExtensions.GetHandle(INativeObject)' is only supported on: 'maccatalyst'.

Thanks, when implicit maccatalyst support added with [SupportedOSPlatform (""ios"")] is suppressed by [UnsupportedOSPlatform (""maccatalyst"")] current logic removes maccatalyst support version but keeps the platform in the list with empty (null) versions. This empty maccatalyst causing this regression, it shows that we should remove this platform completely. By design child (nested) API could narrow platform support, removing empty maccatalyst will just work as pre this scenario. I have updated the code accordingly and added related tests

[rolfbjarne]

CC @ViktorHofer @tannergooding, is this something you guys can approve/merge? I (as the bug reporter) can verify the fix works, I've tested it locally.