staging: Add pointer warp protocol

This global interface allows applications to request the pointer to be moved to a position relative to a wl_surface.

Co-authored by: @Zamundaaa, @mak, @zzag

Fixes: #158

Requirements for merging

• Review
• Implementations (three required)
  • KWin: https://invent.kde.org/plasma/kwin/-/merge_requests/6460
  • Qt: https://invent.kde.org/zamundaaa/qtwayland/-/commits/work/zamundaaa/pointer-warp
  • SDL: https://github.com/libsdl-org/SDL/pull/10922
• ACKs from members (three required)