Add a visual indicator to memory reporting.
This turns the memory reporting button into a slider that fills up with color
as the memory usage increases.
- From 0% to 20% it'll be the themes' highlight color.
- From 20 to 40% it'll mix to turn towards a dark yellow.
- From 40% to 80% it'll mix to turn towards a darker red.
- From 80% onwards it'll be red.
This should help less technical users determine whether their computer can handle what
they're requesting it to do.
CCMAIL:kimageshop@kde.org
Differential Revision: https://phabricator.kde.org/D19167
Ref T10368