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/DiscordSocketClient.cs

@@ -213,6 +213,27 @@ namespace Discord.WebSocket
             base.Dispose(disposing);
         }
 
+
+        internal override async ValueTask DisposeAsync(bool disposing)
+        {
+            if (!_isDisposed)
+            {
+                if (disposing)
+                {
+                    await StopAsync().ConfigureAwait(false);
+
+                    if (!(ApiClient is null))
+                        await ApiClient.DisposeAsync().ConfigureAwait(false);
+
+                    _stateLock?.Dispose();
+                }
+                _isDisposed = true;
+            }
+
+            await base.DisposeAsync(disposing).ConfigureAwait(false);
+        }
+
+        /// <inheritdoc />
         internal override async Task OnLoginAsync(TokenType tokenType, string token)
         {
             if (_shardedClient == null && _defaultStickers.Length == 0 && AlwaysDownloadDefaultStickers)