Enable TelemetryTest (#121498)

Running in EAT mode, locally with Chrome does not reveal any problems.
The failures were deterministic when disabled. Disabling happened just
after emscripten bump to `3.1.12`. Now we are on `3.1.56`.

Reverts:
- #85678
- #109179 (added
`IsBrowserAndIsBuiltWithAggressiveTrimming`)

Fixes #71877, fixes
#109024.

Author: ilonatommy

src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs

@@ -298,7 +298,6 @@ public static bool IsMetadataTokenSupported
         // Changed to `true` when trimming
         public static bool IsBuiltWithAggressiveTrimming => IsNativeAot || IsAppleMobile;
         public static bool IsNotBuiltWithAggressiveTrimming => !IsBuiltWithAggressiveTrimming;
-        public static bool IsBrowserAndIsBuiltWithAggressiveTrimming => IsBuiltWithAggressiveTrimming && IsBrowser;
         public static bool IsTrimmedWithILLink => IsBuiltWithAggressiveTrimming && !IsNativeAot;
 
 #if NET

src/libraries/System.Net.Http/tests/FunctionalTests/TelemetryTest.cs

@@ -22,8 +22,6 @@ public abstract class TelemetryTest : HttpClientHandlerTestBase
         public TelemetryTest(ITestOutputHelper output) : base(output) { }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/71877", typeof(PlatformDetection), nameof(PlatformDetection.IsBrowser), nameof(PlatformDetection.IsMonoAOT))]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/109024", typeof(PlatformDetection), nameof(PlatformDetection.IsBrowserAndIsBuiltWithAggressiveTrimming))]
         public void EventSource_ExistsWithCorrectId()
         {
             Type esType = typeof(HttpClient).Assembly.GetType("System.Net.Http.HttpTelemetry", throwOnError: true, ignoreCase: false);