[KRDB] Rename GTK colours to be exported
Summary:
The colours exported by KRDB for GTK now have the _breeze suffix.
BUG: 417461
FIXED-IN: 5.19
Test Plan: In tandem with D27425, no visual change should be expected.
Reviewers: Plasma, ngraham
Reviewed By: ngraham
Subscribers: ongunkanat, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D27426