Align configure button consistently across delegates

Summary:
Currently the configure button is aligned to the win decoration in the
background. This is bound to 40 - the inactive decorations shadow.

This means the configure button ends up in different places across each
item,
looking a bit weird and potentially not even on top of the right
delegate.

This patch aligns the configure button relative to the overall delegate
so that it's in the same place on every item

Test Plan: Looked at KCM

Reviewers: Plasma

Subscribers: plasma-devel, kwin

Tags: KWin

Differential Revision: https://phabricator.kde.org/D3526

BUG: 372685