Disable mouse by default if no video playback

If video playback is disabled, then SDK mouse (which uses absolute
positions) could not be used, so the default mouse mode was
automatically switched to UHID.

But UHID does not work on all devices, so it could make the whole scrcpy
session fail.

Instead, disable the mouse by default. It is still possible to pass -M
or --mouse=uhid to enable it explicitly.

Fixes #5410 <https://github.com/Genymobile/scrcpy/issues/5410>