fix(Voice*): fix speaking event and voice receive (#3749)

* fix(Voice*): synthesize speaking event from UDP packets

* fix(VoiceReceiver): skip over undocumented Discord byte

See #3555

* fix(VoiceConnection): play frame silence before emitting ready

* typings: account for changes in private api

src/client/voice/util/Silence.js

@@ -0,0 +1,16 @@
+const { Readable } = require('stream');
+
+const SILENCE_FRAME = Buffer.from([0xF8, 0xFF, 0xFE]);
+
+/**
+ * A readable emitting silent opus frames.
+ * @extends {Readable}
+ * @private
+ */
+class Silence extends Readable {
+  _read() {
+    this.push(SILENCE_FRAME);
+  }
+}
+
+module.exports = Silence;