Blender Git Loki

Optimization: Don't compute the snap to face on the knife tool twice

Both `knife_find_closest_vert` and `knife_find_closest_edge` call
`knife_find_closest_face`. Thus, running the raycast twice and setting
values like `kcd->curr.bmface` and `kcd->curr.is_space` repeatedly.

So:
- separate `knife_find_closest_face` from `knife_find_closest_vert` and `knife_find_closest_edge`.
- rename `knife_find_closest_vert` to `knife_find_closest_vert_of_face`
- rename `knife_find_closest_edge `to `knife_find_closest_edge_of_face`.
- do not set parameters previously set.

Differential Revision: https://developer.blender.org/D8198