[effects] Delay creation of EffectFrames in WindowGeometryEffect

Summary:
Without Xwayland KWin starts so fast that the creation of the EffectFrame
triggers a crash in the Wayland integration as the KWin internal
connection isn't fully setup.

To workaround this crash the creation of the EffectFrame is delayed till
the first usage. It doesn't make sense to try to fix the actual crash as
it would require to defer the creation of all Effects.

Test Plan: New test case added which crashes without this fix.

Reviewers: KWin, Plasma

Subscribers: plasma-devel, kwin

Tags: KWin

Differential Revision: https://phabricator.kde.org/D8821