Fixes some issues found by UBSAN and other misc things:
* Fixed memory leak on exit.
* Properly align ray packet buffer to 64 bytes.
* Added some compiler flags from Embree's build system.
* Fixed ray masks.
Minor patch upgrade. Enabling ray packets results in faster
processing of ray streams (i.e. occlusion culling buffer
updates) at the cost of slightly larger binary sizes.
Since Embree v3.13.0 supports AARCH64, switch back to the
official repo instead of using Embree-aarch64.
`thirdparty/embree/patches/godot-changes.patch` should now contain
an accurate diff of the changes done to the library.
Added an occlusion culling system with support for static occluder meshes.
It can be enabled via `Project Settings > Rendering > Occlusion Culling > Use Occlusion Culling`.
Occluders are defined via the new `Occluder3D` resource and instanced using the new
`OccluderInstance3D` node. The occluders can also be automatically baked from a
scene using the built-in editor plugin.
Rémi Verschelde
jfons