Address sanitizer fixes
- Some memory leaks in xdg shells, rootston output and x11 backend
- A use after free in wayland backend.
I'm not 100% happy with my use-after-free fix, if someone has a better idea to access the wlr_wl_pointer from the output destroy handler. At first I wanted to add another output event handler listener to the pointer itself but since the wayland backend can have many outputs and a single pointer (at least with the current design, how does it handle being started from a rootston with multiple seats?) it was more straight-forward to cleanup from output, but I'm sure this can be done better.