FIX: call composer reset with correct params (#21777)

We were calling reset without the proper params which was causing errors in the console. This commit does the following changes:

- ensures `composer.cancel()` is the only way to cancel editing/reply
- adds a `draftSaved` property to chat message to allow for better tests
- writes a spec to ensure the flow is correct
- adds more page objects for better tests
- homogenize the default state of objects on chat message

Co-authored-by: Martin Brennan <martin@discourse.org>

plugins/chat/assets/javascripts/discourse/components/chat-composer.hbs

@@ -22,12 +22,11 @@
       (if this.pane.sending "is-sending")
       (if this.sendEnabled "is-send-enabled" "is-send-disabled")
       (if this.disabled "is-disabled" "is-enabled")
+      (if this.currentMessage.draftSaved "is-draft-saved" "is-draft-unsaved")
     }}
     {{did-update this.didUpdateMessage this.currentMessage}}
     {{did-update this.didUpdateInReplyTo this.currentMessage.inReplyTo}}
     {{did-insert this.setup}}
-    {{did-insert this.didUpdateChannel}}
-    {{did-update this.didUpdateChannel @channel.id}}
     {{will-destroy this.teardown}}
     {{will-destroy this.cancelPersistDraft}}
   >