Blender Git Loki

Sanitize and cleanup a bit depsgraph relations building in some modifiers.

This commit mainly:
* Removes some uneeded dependencies to geometry of other objects (since
we only use positions of those objects...).
* Ensures `DEG_add_modifier_to_transform_relation` is only called once
per modifier (in one case at least it could be called twice).
* For modifiers using texture mask, only add dependencies to object used
to generate texture coordinates when there is actually a texture set.

No behavior change expected from this commit...