Adds a "unstar messages in topic foo" option to the topic sidebar
popover, if there are any starred messages in that topic, known
to the frontend.
Altered existing "unstar all messages" confirmation modal to mention
the topic name, in the case that it was opened by the topic sidebar
codepath.
This is just a v1, and will not unstar old messages from that
topic, if they have not been fetched by the frontend.
Fixes#12194
Co-authored-by: Abhijeet Bodas <abhijeetbodas2001@gmail.com>
This completes the implementation of support for moving a topic to
another stream by adding a basic UI for it.
Fixes#6427, which was previously the most-upvoted issue request in
Zulip.
There are likely to be a bunch of follow-up UI improvements on top of
this change to fully flesh out the feature.