Summary: Wayland has an entire new protocol for getting and setting clipboard when we don't have focus. Unfortunately this means reinventing QClipboard from the QPA.
It uses the newly agreed approach of using QtWayland generated classes in clients directly rather than writing full pimpl API-fixed wrappers first, as ultimately that didn't really help do anything.
Code is written so that it can be moved to KWindowSystem if needed by KDEConnect or others.
The current code blocks when mimeData is fetched. This is in-line with the current XCB integration. I would like to move away, but I think the safest roll out would be to merge as-is get some testers and then iterate.
Test Plan: Copying and pasting all over the place