This commit moves 23 total existing runtime-only properties from the
`UnifiedPaintSettings` struct into the `PaintRuntime` BKE struct. This
shrinks the amount of persisted data by 224 bytes per paint mode per
scene.
In doing this conversion, fields that were previously `char` booleans
have been converted to `bool` types, and C++ math vector types have been
used where appropriate as well.
Some of these attributes may move again in the future to better
distinguish stroke level data from mode level data.
Pull Request: https://projects.blender.org/blender/blender/pulls/141366
fef8c23e9e