2 new repositories: plasma-wayland-protocols and kwayland-server

[Aleix Pol]

Hi everyone,
After long discussions, we have broken kwayland into 3 pieces so we
can work and improve kwin_wayland without having to extend our stable
framework constantly. This of course comes together with an updated
policy with regards to where things should be developed with the goal
of only adding Wayland protocol implementation public interfaces in
the cases that will be shared among several users.

This then includes 2 new repositories:
kdesupport/plasma-wayland-protocols
kde/workspace/kwayland-server

The first should be released independently whenever we have a new
protocol, the latter only together with the rest of Plasma.

Over the next months we'll adapt KWayland as well to depend on
plasma-wayland-protocols and deprecate some of its parts that are now
duplicated.

Anything compiling against kwayland for now is fine and will continue
to work. It still needs to be installed.
All 3 are co-installable.

Sorry for the extra work of caring for the extra repositories. We are
convinced it will be worth it in the long run.

Best regards,
Aleix