Updates warning string when linking to a private stream/channel when
composing a message in the web app to use channel instead of stream.
Updates error banner when using a stream/channel wildcard mention
when composing a message in the web app to use channel instead of
stream.
Part of stream to channel rename project.
Updates a chunk of translated strings that overlap between files,
with the streams settings overlay being the starting point for
finding these strings, to use channel instead of stream.
Part of stream to channel rename project.
This was only used in the undocumented narrow_stream mode, and relied
on a deprecated synchronous XHR request.
Signed-off-by: Anders Kaseorg <anders@zulip.com>