Blender Git Loki

Fix sculpting/painting with viewport clipping and radial symmetry

This was reported for sculpting, the same is true for weightpaint or
vertexpaint though.

When viewport clipping and radial symmetry are enabled, the
'sculpt_brush_test_clipping()' function was not considering radial
symmetry at all, so if the coordinate was outside the clipping planes,
no action would take place. Now the coordinte is brought back to where
the stroke actually happens and that is checked against clipping.

Since other mirroring options while painting/sculpting (as well as
editmode operations with mirroring) usually still take place even if the
mirrored coord is outside the clipping planes, this should also be the
case for radial symmetry.

This grows the 'SculptBrushTest' struct a bit, but should be acceptable?

Fixes T81466

Maniphest Tasks: T81466

Differential Revision: https://developer.blender.org/D9120