compositor: don't spoof events when running as a wayland compositor

Weirdly, clutter stopped segfaulting when we call clutter_x11 methods
and the backend is not right, but this is correct anyway, and
probably fixes some BadDrawable errors in mutter-wayland on x11,
caused by mixing windows of the outer X and windows of Xwayland.
compositor: always redirect passive button grabs to clutter

All WM events (passive button grabs and passive keyboard grabs)
are handled through clutter now, so we must make sure we spoof
them even if they happen on frames (because that's where we
grab on)