feature: Implement Dispose for types which have disposable data (#1171)

* Initial set of dispose implementations

Not handled yet:
- Discord.Net.Websocket/Entities/SocketGuild
- Discord.Net.Tests

* Refactor DiscordSocketClient init into ctor

This way we remove an IDisposableAnalyzer warning for not disposing
the client when we set the client variable.

* Dispose of clients when disposing sharded client

* Finish implementing IDisposable where appropriate

I opted to use NoWarn in the Tests project as it wasn't really necessary
considering that our tests only run once

* Tweak samples after feedback

src/Discord.Net.Commands/CommandService.cs

@@ -27,7 +27,7 @@ namespace Discord.Commands
     ///         been successfully executed.
     ///     </para>
     /// </remarks>
-    public class CommandService
+    public class CommandService : IDisposable
     {
         /// <summary>
         ///     Occurs when a command-related information is received.
@@ -67,6 +67,8 @@ namespace Discord.Commands
         internal readonly LogManager _logManager;
         internal readonly IReadOnlyDictionary<char, char> _quotationMarkAliasMap;
 
+        internal bool _isDisposed;
+
         /// <summary>
         ///     Represents all modules loaded within <see cref="CommandService"/>.
         /// </summary>
@@ -330,9 +332,9 @@ namespace Discord.Commands
 
         //Type Readers
         /// <summary>
-        ///     Adds a custom <see cref="TypeReader" /> to this <see cref="CommandService" /> for the supplied object 
+        ///     Adds a custom <see cref="TypeReader" /> to this <see cref="CommandService" /> for the supplied object
         ///     type.
-        ///     If <typeparamref name="T" /> is a <see cref="ValueType" />, a nullable <see cref="TypeReader" /> will 
+        ///     If <typeparamref name="T" /> is a <see cref="ValueType" />, a nullable <see cref="TypeReader" /> will
         ///     also be added.
         ///     If a default <see cref="TypeReader" /> exists for <typeparamref name="T" />, a warning will be logged
         ///     and the default <see cref="TypeReader" /> will be replaced.
@@ -607,5 +609,23 @@ namespace Discord.Commands
                 await _commandExecutedEvent.InvokeAsync(chosenOverload.Key.Command, context, result);
             return result;
         }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (!_isDisposed)
+            {
+                if (disposing)
+                {
+                    _moduleLock?.Dispose();
+                }
+
+                _isDisposed = true;
+            }
+        }
+
+        void IDisposable.Dispose()
+        {
+            Dispose(true);
+        }
     }
 }