Merge remote-tracking branch 'mdroth/qga-win32-pull-2-23-12' into staging

Merge remote-tracking branch 'mdroth/qga-win32-pull-2-23-12' into staging

* mdroth/qga-win32-pull-2-23-12:
  qemu-ga: add win32 guest-shutdown command
  qemu-ga: add Windows service integration
  qemu-ga: add initial win32 support
  qemu-ga: fixes for win32 build of qemu-ga
  qemu-ga: rename guest-agent-commands.c -> commands-posix.c
  qemu-ga: separate out common commands from posix-specific ones
  qemu-ga: move channel/transport functionality into wrapper class
  qemu-ga: Add schema documentation for types