Now we have a better distinction of what is snap to grid and what is
snap to increments.
The code also allows the implementation of mixed snap for these modes.
Follow up of b2ee1770d4c3 and 10c2254d412d, 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.
