tts throttling and send user_interruption event (#1019)

* tts throttling and send user_interruption event

* tts streaming: if we get a flush with tokens pending, send the flush after the tokens

* wip

lib/session/call-session.js

@@ -866,6 +866,8 @@ class CallSession extends Emitter {
     }
   }
   clearTtsStream() {
+    this.requestor?.request('tts:streaming-event', '/streaming-event', {event_type: 'user_interruption'})
+      .catch((err) => this.logger.info({err}, 'CallSession:clearTtsStream - Error sending user_interruption'));
     this.ttsStreamingBuffer?.clear();
   }