Without this patch, changing the application color scheme from system
settings only affects some widgets. Notably, checkboxes highlighting
colors stays the old color, leading to a hodge-podge color scheme and
bad contrast on some items.
The breeze QStyle caches the colors read via KSharedConfig, so it needs
to re-read the configuration when the application color changes.
QApplication emits an event (originating in KGlobalSettings), which we
can react to.
This fixes the coloring of various widgets in breeze right after color
changes.
BUG:408416
FIXED-IN: 5.15.6