Fix OperationCancelledException and add IAsyncEnumerable to wait without thread blocking (#1562)

* Fixed Task Scheduler operation cancelled error caused by Orphaned RunCleanup task on RequestQueue not being awaited on dispose

* Added async disposable interface to various components

* Added incorrect early marking of disposed for DiscordSocketApi client

* Added general task canceled exception catch to cleanup task

* Fix merge errors

Co-authored-by: Quin Lynch <49576606+quinchs@users.noreply.github.com>
Co-authored-by: quin lynch <lynchquin@gmail.com>

src/Discord.Net.WebSocket/DiscordSocketApiClient.cs

@@ -124,12 +124,39 @@ namespace Discord.API
                     _decompressor?.Dispose();
                     _compressed?.Dispose();
                 }
-                _isDisposed = true;
             }
 
             base.Dispose(disposing);
         }
 
+#if NETSTANDARD2_1
+        internal override async ValueTask DisposeAsync(bool disposing)
+#else
+        internal override ValueTask DisposeAsync(bool disposing)
+#endif
+        {
+            if (!_isDisposed)
+            {
+                if (disposing)
+                {
+                    _connectCancelToken?.Dispose();
+                    (WebSocketClient as IDisposable)?.Dispose();
+#if NETSTANDARD2_1
+                    if (!(_decompressor is null))
+                        await _decompressor.DisposeAsync().ConfigureAwait(false);
+#else
+                    _decompressor?.Dispose();
+#endif
+                }
+            }
+
+#if NETSTANDARD2_1
+            await base.DisposeAsync(disposing).ConfigureAwait(false);
+#else
+            return base.DisposeAsync(disposing);
+#endif
+        }
+
         public async Task ConnectAsync()
         {
             await _stateLock.WaitAsync().ConfigureAwait(false);