shell: Honor modal dialogs and full screen when raising top-bar

Just handling the fader isn't enough as we want full screen windows and modal dialogs to stretch over the top bar as well.

We have some more cases like screenshost screen flash but that needs proper z-level which we can introduce once the layer-shell-effects is in. Same if we want system modal dialogs on the lock screen.

Fixes: 55bbe575

Signed-off-by: Guido Günther guido.gunther@puri.sm

Relies on phoc!370 (merged) so that needs to go in first hence draft - also because I've only tested the trivial case so far.

Closes: #764 (closed)