Fractional scaling hack: Push decoration slightly under client if decoration is named "breeze"

Hack for Plasma 6.1 until fractional scaling borders are fixed.

Backport of: !56 (merged)

decoration: Only apply hack on windows with outlines

Since the hack is only applied with window outlines, do same in kdecoration.

This also seems to fix most issues with maximized windows having gaps and such.

Issue mentioned in here: breeze!431 (comment 880658)