[Xwayland 22.1] Backport fixes
This backports:
- a7364193 os: print if unw_is_signal_frame()
- dc8162d5 os: print registers in the libunwind version of xorg_backtrace()
- b9b33d88 xwayland/present: Do not send two idle notify events for flip pixmaps
- 92a00f52 xwayland: Fix check logic in sprite_check_lost_focus()
- 2ec7c168 xwayland: Change randr_output status when call xwl_output_remove()
The first two commits are not actual fixes, but may be useful for debugging.