[kstyle] Implement window moving on Wayland

Summary:
So far breeze hard disabled the window moving on Wayland. With this
change the required functionality gets added.

For that Breeze creates an additional Seat and a Pointer on it to track
all pointer button events on the window. That way the kstyle gets the
latest serial which needs to be passed to the move requests. This is not
available through QtWayland's native interface, thus Breeze needs to
interact with Wayland directly.

When the move is triggered Breeze gets the ShellSurface for the window
and triggers the move on the own Seat object with the tracked serial.

Test Plan: Tested with KWin and Weston, move triggered in both.

Reviewers: #plasma_on_wayland

Subscribers: plasma-devel

Tags: #plasma_on_wayland

Differential Revision: https://phabricator.kde.org/D3019