We update the pills typeahead logic to also include
stream results and pass the "stream" key in `opts`
to enable this option for the Add subscriber form.
This commit implements the feature of adding all the
subscribers of another stream in the "Add subscribers"
UI, with the help of a new "stream_pill.js` file.
We temporarily add `user_pill.js` to the EXEMPT_FILES
list as typeahead will be set up in `stream_edit.js`
file which does not have any dedicated tests file.
Work towards #15186.
This commit changes the stream settings UI for adding subscribers to
use our standard user pills in the input box, rather than just
plain-text email addresses. This is important progress towards
removing display email addresses from the Zulip UI.
It also allows subscribing multiple users at the same time, which is a
nice improvement.
Commit 68335d9124 removed the ability to tab
into this field, since it was a hidden field. This field is no longer
hidden, and this commit restores the ability to tab into it.