Instead of displaying contextual options in the message buttons popover
based on the message type, we instead abstract the logic behind the
scenes and instead just show the "Start new conversation" with the
relevant hotkey hint.
This also removes the `is_in_private_narrow` parameter which now serves
no purpose in the popover template, as we display the
"New direct message" option in all cases.
As part of the popover menu redesign, this redesigns the mobile message
buttons popover using the new "popover-menu" tippy theme and improves
accessibility by using appropriate ARIA attributes.
Fixes part of #28699.
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.
Sayam Samal
Lauryn Menard
Karl Stolley
Aman Agrawal