Historically, the `UnifiedPaintSettings` struct has been used to
provide users the ability to set brush values at a scene level. Examples
of such attributes are the brush size, strength, and color, to name a
few.
Instead of these values being shared across all of the grease pencil,
mesh painting, and curves sculpting modes. This commit migrates the
data to the `Paint` struct, meaning that each individual mode (e.g.
Sculpt, Vertex Paint, Grease Pencil Draw) now has the ability to change
these values without affecting other modes.
While this change is large, the majority of the work is simply
refactoring access to the `UnifiedPaintSetting` struct. to ensure the
correct property is being retrieved.
Resolves#134077
Pull Request: https://projects.blender.org/blender/blender/pulls/139766
4434a30d40