Fix timeout token registration disposal

This prevents a bunch of InvalidOperationExceptions from being thrown when a timeout is logged without an active test.

test/Nerdbank.Streams.Tests/MultiplexingStreamPerfTests.cs

@@ -42,6 +42,7 @@ public ValueTask DisposeAsync()
     {
         this.serverPipe.Dispose();
         this.clientPipe.Dispose();
+        this.Dispose();
         return default;
     }
 

test/Nerdbank.Streams.Tests/MultiplexingStreamSeededChannelTests.cs

@@ -74,6 +74,8 @@ public async ValueTask DisposeAsync()
 
         this.mx1?.TraceSource.Listeners.OfType<XunitTraceListener>().SingleOrDefault()?.Dispose();
         this.mx2?.TraceSource.Listeners.OfType<XunitTraceListener>().SingleOrDefault()?.Dispose();
+
+        this.Dispose();
     }
 
     [Fact]

test/Nerdbank.Streams.Tests/MultiplexingStreamTests.cs

@@ -49,6 +49,8 @@ public async ValueTask DisposeAsync()
 
         this.mx1?.TraceSource.Listeners.OfType<XunitTraceListener>().SingleOrDefault()?.Dispose();
         this.mx2?.TraceSource.Listeners.OfType<XunitTraceListener>().SingleOrDefault()?.Dispose();
+
+        this.Dispose();
     }
 
     [Fact, Obsolete]

test/Nerdbank.Streams.Tests/NestedPipeReaderTests.cs

@@ -19,7 +19,11 @@ public NestedPipeReaderTests(ITestOutputHelper logger)
     {
     }
 
-    public ValueTask DisposeAsync() => default;
+    public ValueTask DisposeAsync()
+    {
+        this.Dispose();
+        return default;
+    }
 
     public async ValueTask InitializeAsync()
     {

test/Nerdbank.Streams.Tests/TestBase.cs

@@ -66,6 +66,7 @@ protected TestBase(ITestOutputHelper logger)
 
     public void Dispose()
     {
+        this.timeoutLoggerRegistration.Dispose();
         this.Dispose(true);
         GC.SuppressFinalize(this);
     }