Blender Git Loki

Fix T65620: Sculpting brush size jumping.

The PBVHs raycast function calls `isect_ray_tri_epsilon_v3` with epsilon `0.1` which is inaccurate and may result in the problem presented in T65620.
The solution is to use `isect_ray_tri_watertight_v3` instead `isect_ray_tri_epsilon_v3`.
This can positively affect other areas as well.

Reviewers: brecht, campbellbarton

Differential Revision: https://developer.blender.org/D5083