cursor-shape-v1: new protocol

This is based on the Chromium protocol 1.

Closes: #58 (closed)
References: !21 (closed)

• Review (@zzag)
• ACKs
  • wlroots (@emersion)
  • KDE (@zzag)
  • Weston (@daniels)
• 3 implementations
  • wlroots: wlroots/wlroots!4106
  • KDE: https://invent.kde.org/plasma/kwin/-/merge_requests/4060
  • Smithay client toolkit: https://github.com/Smithay/client-toolkit/pull/381
  • Qt: https://codereview.qt-project.org/c/qt/qtwayland/+/477172