Refactors the BVH to make it more generic and customizable. Instead of hard coding the system of pairable_mask and pairable_type into the BVH, this information is no longer stored internally, and instead the BVH uses callbacks both for determining whether pairs of objects can pair with each other, and for filtering cull / intersection tests.
In addition, instead of hard coding the number of trees, the BVH now supports up to 32 trees, and each object can supply a tree collision mask to determine which trees it can collide against.
This enables the BVH to scale to either the two or 3 trees needed in physics, and the single tree used without pairing in Godot 4 render tree.
The BVH implementation is not checking collision layers on existing
pairs on move like other physics broadphases do.
This is solved by adding a new call to trigger pair callbacks again so
the physics engine can check layers again (specific to the BVH version,
other broadphase implementations just trigger a move like before).
Dynamic BVH doesn't update the tree anymore when calling set_pairable
with no parameter change.
Also modified Godot Physics broadphase to create objects directly with
pairable (static) set correctly to make use of this optimization for the
BVH broadphase.
Note: Octree broadphase doesn't use this optimization because it forces
an update on move, so passing the proper AABB and static parameters on
creation would cause the tree to update twice.
When set_static is called on a newly added object, the forced collision
check in BVH set_pairable was using an empty AABB, which caused
unnecessary collision checks at the origin, then a call to move was
checking again at the right position.
These changes ensure broadphase objects are added to the BVH tree with
proper AABB so collision checks are correctly done right away.
Octree & Basic broadphase trees are not affected by these changes.
Complete rewrite of spatial partitioning using a bounding volume hierarchy rather than octree.
Switchable in project settings between using octree or BVH for rendering and physics.
