Allow skipping vertex duplicates on Ammo mesh generation

[LeXXik]

Forum: https://forum.playcanvas.com/t/much-faster-collision-mesh-building-without-removeduplicatevertices/33488/1

This is a feature request to allow skipping the removal of duplicate vertices during a collision mesh generation. According to the OP find, it seems to have a potential to improve the trimesh generation time.

At the moment, the engine forces Ammo to loop through the vertices to find and remove the duplicates here (true flag):

engine/src/framework/components/collision/system.js

Line 373 in e815adf

triMesh.addTriangle(v1, v2, v3, true);

[LeXXik]

Benchmarking and implementation option:
https://playcanvas.com/project/1153025/overview/collision-mesh-benchmark