minimize dialog resizes/moves

Summary:
take into account size hints also when adjusting with synctomainitemsize
which sometimes has to be executed right before adjusting from the layout
hints, giving one wrong resize

introduce geometryUpdatesBlocked, which stops the dialog
from syncing which is useful when both visual parent and item
contents gets updated in one go (the tooltip) it is not
yet exported to qml and it shouldn't as is dangerous, but
kicker may make use of it between changing the submenu model and
the visualparent

alternative implementations may be:

• a method that takes both main item and visual parent
• delaying with a timer setGeometry (ouch)

this part can also be left behind for now and see if the rest is good enough

Test Plan:
no visual glitches visible anymore in wayland when moving the tooltip
in the taskbar, x11 ok too

Reviewers: Plasma, hein, davidedmundson

Reviewed By: Plasma, hein, davidedmundson

Subscribers: broulik, davidedmundson, plasma-devel, Frameworks

Tags: Plasma, Frameworks

Differential Revision: https://phabricator.kde.org/D5912