Support custom-data correction based on surrounding geometry for all
transformation modes of the mesh transform operators.
The is the same logic used in Vert and Edge Slide.
In order not to change the current default behavior,
this property does not affect Vert and Edge Slide modes.
- Use `t->spacemtx` as the orientation matrix instead `t->orient_matrix`.
- Unify constraint behavior between modal and non-modal.
- Simplify code to remove old workarounds and rearrange struct members.
This fix T66142 since the actual `orient_type` (in the case
`V3D_ORIENT_NORMAL`) is used during Redo instead of always using
`V3D_ORIENT_CUSTOM_MATRIX`).
Differential Revision: https://developer.blender.org/D7469
Follow up of b2ee1770d4 and 10c2254d41, part of T74432.
Now the area and region naming conventions should be less confusing.
Mostly a careful batch rename but had to do few smaller fixes.
Also ran clang-format on affected files.
