fix: Add DeleteMessagesAsync to IVoiceChannel (#2367)

Also adds remaining rate-limit information to client log.

src/Discord.Net.Core/Entities/Channels/IVoiceChannel.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 
 namespace Discord
@@ -25,6 +26,44 @@ namespace Discord
         /// </returns>
         int? UserLimit { get; }
 
+        /// <summary>
+        ///     Bulk-deletes multiple messages.
+        /// </summary>
+        /// <example>
+        ///     <para>The following example gets 250 messages from the channel and deletes them.</para>
+        ///     <code language="cs">
+        ///     var messages = await voiceChannel.GetMessagesAsync(250).FlattenAsync();
+        ///     await voiceChannel.DeleteMessagesAsync(messages);
+        ///     </code>
+        /// </example>
+        /// <remarks>
+        ///     This method attempts to remove the messages specified in bulk.
+        ///     <note type="important">
+        ///         Due to the limitation set by Discord, this method can only remove messages that are posted within 14 days!
+        ///     </note>
+        /// </remarks>
+        /// <param name="messages">The messages to be bulk-deleted.</param>
+        /// <param name="options">The options to be used when sending the request.</param>
+        /// <returns>
+        ///     A task that represents the asynchronous bulk-removal operation.
+        /// </returns>
+        Task DeleteMessagesAsync(IEnumerable<IMessage> messages, RequestOptions options = null);
+        /// <summary>
+        ///     Bulk-deletes multiple messages.
+        /// </summary>
+        /// <remarks>
+        ///     This method attempts to remove the messages specified in bulk.
+        ///     <note type="important">
+        ///         Due to the limitation set by Discord, this method can only remove messages that are posted within 14 days!
+        ///     </note>
+        /// </remarks>
+        /// <param name="messageIds">The snowflake identifier of the messages to be bulk-deleted.</param>
+        /// <param name="options">The options to be used when sending the request.</param>
+        /// <returns>
+        ///     A task that represents the asynchronous bulk-removal operation.
+        /// </returns>
+        Task DeleteMessagesAsync(IEnumerable<ulong> messageIds, RequestOptions options = null);
+
         /// <summary>
         ///     Modifies this voice channel.
         /// </summary>