- 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
