Instead of selecting a screen to share arbitrarily, we'll now allow user
to select the screen to share. Note that sharing multiple screens at the
time is still not supported (though prolly not too far-fetched).
Related to #4666

Release Notes:
- Added screen selector dropdown to screen share button
---------
Co-authored-by: Kirill Bulatov <kirill@zed.dev>
Co-authored-by: Cole Miller <cole@zed.dev>
Reapplies #27807 after [revert due to not building on
ARM](https://github.com/zed-industries/zed/pull/28141) by updating scap
to include [a fix to its build on
ARM](08f0a01417)
Release Notes:
- N/A
---------
Co-authored-by: Marshall Bowers <git@maxdeviant.com>
While `scap` does have support for Wayland and Windows, but haven't seen
screensharing work properly there yet. So for now just adding support
for X11 screensharing.
WIP branches for enabling wayland and windows support:
* https://github.com/zed-industries/zed/tree/wayland-screenshare
* https://github.com/zed-industries/zed/tree/windows-screenshare
Release Notes:
- Added support for screensharing on X11 (Linux)
---------
Co-authored-by: Conrad <conrad@zed.dev>
Co-authored-by: Mikayla <mikayla@zed.dev>
Co-authored-by: Junkui Zhang <364772080@qq.com>