Implement wlr-data-control-unstable-v1
Introduce public API to manage clipboards from external sources (klipper etc) As this is all handled internally within kwayland-server some level of abstraction was needed within kwayland-server.
To do this a class that covers the concept of a clipboard was introduced which represents the contents of a clipboard.
Two potential discussion points: It's the old way without qtwayland-scanner as it was started a year ago, but blocked on the abstracting part. It could be changed, and also renamed to WlrDataControlUnstableV1 or whatever? Given it's all handled internally, I kinda don't see the point of exporting the class (other than the manager) at all?