[NavMesh Pathfinding] Add a non-blocking padding property

[D8H]

Description

• A feature request on this feature: NavMesh pathfinding behavior #2856
• The user wants the path to be farther from the obstacles to be a bit more natural.
• If the user set a bigger extraBorder, some paths may no longer be usable.

Functional solution

• Add a non-blocking padding property.
• Paths must stay about the same length (no detour).
• Origin and target of the path should not be impacted by it.

Technical solution 1: dichotomy

• Try to find a paths on 2 NavMeshes
  • one without the extra padding
  • one with the extra padding
• If the paths length is about the same, use the one with the extra padding.
• Otherwise, dichotomically loop on NavMeshes to find the best NavMesh to use.

The issue with this method is that:

• It may need a lot of NavMeshes instead of just one if the objects are all the same size.
• The whole path will use the same extra padding (sometimes far away from obstacles, sometimes near them).

Technical solution 2: bridge rebuilding

• Tweak the NavMesh to keep the passages that would be blocked by the extra padding.
• Process 2 NavMesh
  • one without the extra padding
  • one with the extra padding
• Maybe use some kind of the cohesiveness analysis to find blocked passages.
• Add the missing bridges on the NavMesh with the extra padding.