Fixes#2467.
This commit introduces seat_get_focus_inactive_floating to supplement
seat_get_focus_inactive_tiling, and uses it during `focus mode_toggle`
which fixes a focus bug.
This also refactors the seat_get_focus_inactive functions so that they
do their selection logic themselves rather than offloading it to
seat_get_focus_by_type which was getting bloated. seat_get_focus_by_type
is now removed.
Lastly, this commit changes seat_get_focus to just return the first
container in the focus stack rather than looping and calling
seat_get_focus_by_type.
3a888163a0