use PlatformSpecific attribute to supress platform specific Quic tests

[wfurt]

Using ConditionalFact creates noise on platforms where given test would never run.

   ===========================================================================================================
  ~/github/wfurt-runtime2/artifacts/bin/System.Net.Quic.Functional.Tests/Debug/net8.0-osx ~/github/wfurt-runtime2/src/libraries/System.Net.Quic/tests/FunctionalTests
    Discovering: System.Net.Quic.Functional.Tests (method display = ClassAndMethod, method display options = None)
    Discovered:  System.Net.Quic.Functional.Tests (found 4 of 122 test cases)
    Starting:    System.Net.Quic.Functional.Tests (parallel test collections = on, max threads = 16)
      System.Net.Quic.Tests.MsQuicPlatformDetectionTests.SupportedLinuxPlatformsWithMsQuic_IsSupportedIsTrue [SKIP]
        Condition(s) not met: "IsLinux"
      System.Net.Quic.Tests.MsQuicPlatformDetectionTests.SupportedWindowsPlatforms_IsSupportedIsTrue [SKIP]
        Condition(s) not met: "IsWindows", "SupportsTls13"
      System.Net.Quic.Tests.MsQuicPlatformDetectionTests.SupportedLinuxPlatforms_IsSupportedIsTrue [SKIP]
        Condition(s) not met: "IsLinux", "IsInHelix"
    Finished:    System.Net.Quic.Functional.Tests
  === TEST EXECUTION SUMMARY ===
     System.Net.Quic.Functional.Tests  Total: 4, Errors: 0, Failed: 0, Skipped: 3, Time: 3.639s
  ~/github/wfurt-runtime2/src/libraries/System.Net.Quic/tests/FunctionalTests

The PlatformSpecific attributes allows to silently suppress tests that are not even candidates

  ~/github/wfurt-runtime2/artifacts/bin/System.Net.Quic.Functional.Tests/Debug/net8.0-osx ~/github/wfurt-runtime2/src/libraries/System.Net.Quic/tests/FunctionalTests
    Discovering: System.Net.Quic.Functional.Tests (method display = ClassAndMethod, method display options = None)
    Discovered:  System.Net.Quic.Functional.Tests (found 1 of 122 test case)
    Starting:    System.Net.Quic.Functional.Tests (parallel test collections = on, max threads = 16)
    Finished:    System.Net.Quic.Functional.Tests
  === TEST EXECUTION SUMMARY ===
     System.Net.Quic.Functional.Tests  Total: 1, Errors: 0, Failed: 0, Skipped: 0, Time: 2.981s

so we have less noise and possibly less entries in test database.

[ghost]

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Issue Details

---

Using ConditionalFact creates noise on platforms where given test would never run.

   ===========================================================================================================
  ~/github/wfurt-runtime2/artifacts/bin/System.Net.Quic.Functional.Tests/Debug/net8.0-osx ~/github/wfurt-runtime2/src/libraries/System.Net.Quic/tests/FunctionalTests
    Discovering: System.Net.Quic.Functional.Tests (method display = ClassAndMethod, method display options = None)
    Discovered:  System.Net.Quic.Functional.Tests (found 4 of 122 test cases)
    Starting:    System.Net.Quic.Functional.Tests (parallel test collections = on, max threads = 16)
      System.Net.Quic.Tests.MsQuicPlatformDetectionTests.SupportedLinuxPlatformsWithMsQuic_IsSupportedIsTrue [SKIP]
        Condition(s) not met: "IsLinux"
      System.Net.Quic.Tests.MsQuicPlatformDetectionTests.SupportedWindowsPlatforms_IsSupportedIsTrue [SKIP]
        Condition(s) not met: "IsWindows", "SupportsTls13"
      System.Net.Quic.Tests.MsQuicPlatformDetectionTests.SupportedLinuxPlatforms_IsSupportedIsTrue [SKIP]
        Condition(s) not met: "IsLinux", "IsInHelix"
    Finished:    System.Net.Quic.Functional.Tests
  === TEST EXECUTION SUMMARY ===
     System.Net.Quic.Functional.Tests  Total: 4, Errors: 0, Failed: 0, Skipped: 3, Time: 3.639s
  ~/github/wfurt-runtime2/src/libraries/System.Net.Quic/tests/FunctionalTests

The PlatformSpecific attributes allows to silently suppress tests that are not even candidates

  ~/github/wfurt-runtime2/artifacts/bin/System.Net.Quic.Functional.Tests/Debug/net8.0-osx ~/github/wfurt-runtime2/src/libraries/System.Net.Quic/tests/FunctionalTests
    Discovering: System.Net.Quic.Functional.Tests (method display = ClassAndMethod, method display options = None)
    Discovered:  System.Net.Quic.Functional.Tests (found 1 of 122 test case)
    Starting:    System.Net.Quic.Functional.Tests (parallel test collections = on, max threads = 16)
    Finished:    System.Net.Quic.Functional.Tests
  === TEST EXECUTION SUMMARY ===
     System.Net.Quic.Functional.Tests  Total: 1, Errors: 0, Failed: 0, Skipped: 0, Time: 2.981s

so we have less noise and possibly less entries in test database.

Author:	wfurt
Assignees:	wfurt
Labels:	test-enhancement, area-System.Net.Quic
Milestone:	-