Rename Transparent background config options
Summary:
This makes the meaning of this option more clear. It also uses the
correct term "checkerboard" instead of "check board".
I have left the RasterImageView::AlphaBackground* terminology the same
as I believe it makes more sense as is in terms of what the code does.
For example AlphaBackgroundNone means we do not draw a background or
draw a transparent background.
Depends on D11630
Before:
After:
Test Plan: Ensure all transparent background options continue to function.
Reviewers: Gwenview, rkflx, ngraham
Reviewed By: Gwenview, rkflx
Tags: Gwenview
Differential Revision: https://phabricator.kde.org/D11824