[iOS][libraries] Skip failing iOS tests with ActiveIssues and proj level skips

[mdh1418]

In effort to assess the state of the iOS library tests, a number of tests will be skipped

Test suites that crash, hang, or have a significant number of failures (mostly 20+ failing unique test methods) are skipped on at the tests.proj level. Otherwise, [ActiveIssue] attributes have been attached to either the individual test methods that fail or the entire class if the whole test class fails. Any pre-existing ActiveIssue attribute associated with iOS had been reassessed to either remain or be closed.

A few test suites have been skipped because they fail with some form of PlatformNotSupportedException. [SkipOnPlatform] attributes are attached to the failing test methods.

All of the Issues can be tracked at https://github.com/dotnet/runtime/projects/48#column-9236436

The ActiveIssues and tests.proj exclusions have been tested on #49917 as well.

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This PR makes the following changes in the following files:
src/libraries/System.IO.Ports/tests/System.IO.Ports.Tests.csproj - Removed $(NetCoreAppCurrent)-iOS from target frameworks as it is stated to currently only supported on Windows.

src/libraries/tests.proj - Update the test suites that need to be skipped at the project level, reducing the number and categorizing as a skip due to PNSE, a skip due to numerous failures, and a skip due to the suite crashing.

The remaining files changed are either:
[ActiveIssue("<issue-url>", TestPlatforms.iOS | TestPlatforms.tvOS | TestPlatforms.MacCatalyst)]
[SkipOnPlatform(TestPlatforms.iOS | TestPlatforms.tvOS, "Not supported on iOS or tvOS.")]

[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]

A few test suites have been skipped because they fail with some form of PlatformNotSupportedException.

Which are they?

[mdh1418]

@marek-safar So far the PNSE failure test suites being completely skipped are System.Console.Tests.csproj, System.IO.FileSystem.Tests.csproj, System.Security.Cryptography.OpenSsl.Tests.csproj, System.Threading.Thread.Tests.csproj. There is some more consolidation and checking to be done, especially since tests cannot run to completion related to https://github.com/dotnet/core-eng/issues/12969

There are some test facts that fail with PNSE that are skipped individually, I'll need to ensure that they're being tracked/marked with some note of PNSE.

[marek-safar]

Out of these 4 I think only System.Security.Cryptography.OpenSsl.Tests.csproj should be skipped completely.

[tqiu8]

On my local machine System.Threading.Thread is passing.

[mdh1418]

@tqiu8 when you ran System.Threading.Thread.Tests, was that including this commit? ca51de9 (Which skips the test facts)

[mdh1418]

@marek-safar Of all the previous CI runs of iOS and tvOS, the following suites have the following number of methods that fail with PNSE. Should System.Security.Cryptography.X509Certificates.Tests also be skipped completely?

System.Console.Tests.dll - 46
System.Diagnostics.Process.Tests.dll - 12
System.IO.FileSystem.Tests.dll - 3 
System.Net.NetworkInformation.Functional.Tests.dll - 1 
System.Net.Ping.Functional.Tests.dll - 25 
System.Security.Cryptography.OpenSsl.Tests.dll - 726
System.Security.Cryptography.X509Certificates.Tests.dll - 163
System.Security.Cryptography.Xml.Tests.dll - 3 
System.Runtime.Extensions.Tests.dll - 1
System.Threading.Thread.Tests.dll - 1
System.Xml.RW.XmlReader.Tests.dll - 3 

all_ios_tvos_PNSE_us.txt

[tqiu8]

@tqiu8 when you ran System.Threading.Thread.Tests, was that including this commit? ca51de9 (Which skips the test facts)

Yep, that's probably what happened.

[marek-safar]

Should System.Security.Cryptography.X509Certificates.Tests also be skipped completely?

Preferably not

[akoeplinger]

Yup sounds good, but we'll still go ahead and merge this PR for now to get to a green state in runtime-staging :)