[shadow] Rebuild quads after creation of shadow
Summary:
If a shadow is installed for already rendered window, the shadow won't
be initially rendered because we don't rebuild window quad cache.
BUG: 398572
FIXED-IN: 5.14.0
Test Plan: Can't reproduce 398572 anymore.
Reviewers: KWin, davidedmundson
Reviewed By: KWin, davidedmundson
Subscribers: kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D15475