[Performance] Optimize mesh visibility checks in RFMesh for better performance

[jfranmatheu]

Optimize mesh visibility compute

Related issues: #842 - #1246 - #1423

As the mesh geometry grows, the access to visible_verts, visible_edges and visible_faces is quite time spending, taking precious seconds of time and lastly, lagging the tools. Tools make use of this to know which geometry it can affect to and it can have a great impact when entering the tool, start a tool action and confirm a tool action (you may find different effect depending on the tool as there are many factors involved).

Implications

• Laggy Tools
• Bad user experience (no interactive tools + long waits = frustration)

Proposed Solution

1. [DONE] Improving current functions logic: this can speed up visible_edges and visible_faces by just making a better use of visible verts.
2. Improvements on the visible_verts logic (and all around is_vis and xform)

• Use a more efficient structure to compute several data.
• Multi-processing.
• Cython, CPython or similar.
• Caching and partial-updating.

[jfranmatheu]

I re-open this issue since I'm looking into better related improvements