Partial redrawing of the 3d viewport has not worked since the transition
to 2.8. Despite this, we still calculate the paint BVH bounds of the
affected area.
To avoid this wasted work and simplify the code, we remove the related
functions. Further work to enable partial redraws would not necessarily
be integrated in the same way. Additionally, a minor speedup of 1.05x
(1.00ms to 0.95ms) can be observed with this commit when performing
weight painting on a mesh with 2 million elements.
Similar to #136471
Pull Request: https://projects.blender.org/blender/blender/pulls/136912
795e63a4c7