Previously notifications.clear_compose_notifications was used accross
the codebase. Since introducing the new
compose_banner.clear_message_sent_banners function, the two functions
are similar enough that we can just use clear_message_sent_banners
everywhere. This commit also moves scroll_to_message_banner_message_id
to compose_banner.
Instead of removing all compose banners, we now remove only warnings
and errors -- this makes no difference right now, but this change
will allow us to add other compose banners that are cleared at
different times.
evykassirer