Use Platform-Guard Assertion Annotations for some known cases

[buyaa-n]

As part of #44922 now we have Platform-Guard Assertion Annotation attributes added to libraries and the Platform Compatibility Analyzer now supports them. So its time to use SupportedOSPlatformGuard and UnsupportedOSPlatformGuard whenever needed

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[marek-safar]

I think there are a few more cases that could be probably annotated. For example one for consideration is SocketsHttpHandler.IsSupported and there was something in crypto too

[MaximLipnin]

@buyaa-n One question just for my information:

How could I use these guards to annotate the APIs which partly throw PNSE based on some condition, e.g. https://github.com/dotnet/runtime/blob/main/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketPal.Unix.cs#L32-L38 ? The methods using this one throw on ios/tvos (and a couple of related System.Net.NetworkInformation.Functional.Tests tests fail).

[buyaa-n]

I think there are a few more cases that could be probably annotated. For example one for consideration is SocketsHttpHandler.IsSupported and there was something in crypto too

Thanks, i remember SocketsHttpHandler.IsSupported i will add that, but i don't think ever heard about crypto one

[buyaa-n]

How could I use these guards to annotate the APIs which partly throw PNSE based on some condition, e.g. https://github.com/dotnet/runtime/blob/main/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketPal.Unix.cs#L32-L38 ? The methods using this one throw on ios/tvos (and a couple of related System.Net.NetworkInformation.Functional.Tests tests fail).

Not sure, from the code in the link it doesn't look like it does platform check, seems doing capabilities check

The methods using this one throw on ios/tvos (and a couple of related System.Net.NetworkInformation.Functional.Tests tests fail)

That sound like its need UnsupportedOSPlatform on ios/tvos attributes (not guard attributes)

[ManickaP]

Please do not reuse _http3Enabled for the guard. Add a new IsHttp3Supported as @marek-safar suggests.

[ManickaP]

Thanks!