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.
* Particle shaders now have start() and process()
* Particle collision happens between them.
* The RESTART property is kept, so porting an old shader is still possible.
This fixes the problem of particle collisions not functioning on the first particle frame.
-Used a more consistent set of keywords for the shader
-Remove all harcoded entry points
-Re-wrote the GLSL shader parser, new system is more flexible. Allows any entry point organization.
-Entry point for sky shaders is now sky().
-Entry point for particle shaders is now process().
-Advanced Settings toggle also hides advanced properties when disabled
-Simplified Advanced Bar (errors were just plain redundant)
-Reorganized rendering quality settings.
-Reorganized miscelaneous settings for clean up.
-Rendering server now uses a split RID allocate/initialize internally, this allows generating RIDs immediately but initialization to happen later on the proper thread (as rendering APIs generally requiere to call on the right thread).
-RenderingServerWrapMT is no more, multithreading is done in RenderingServerDefault.
-Some functions like texture or mesh creation, when renderer supports it, can register and return immediately (so no waiting for server API to flush, and saving staging and command buffer memory).
-3D physics server changed to be made multithread friendly.
-Added PhysicsServer3DWrapMT to use 3D physics server from multiple threads.
-Disablet Bullet (too much effort to make multithread friendly, this needs to be fixed eventually).
Inverted the spotlight angle attenuation so a higher value results in
a dimmer light, this makes it more consistent with the distance
attenuation.
Also changed the way spotlighs are computed in SDFGI
and GIPorbes and GPU lightmapper, now it matches the falloff used in the scene rendering
code.
-Always use temporal reproject, it just loos way better than any other filter.
-By always using termporal reproject, the shadowmap reduction can be done away with, massively improving performance.
-Disadvantage of temporal reproject is update latency so..
-Made sure a gaussian filter runs in XY after fog, this allows to keep stability and lower latency.
-Added more finegrained control in RenderingDevice API
-Optimized barriers (use less ones for thee same)
-General optimizations
-Shadows render all together unbarriered
-GI can render together with shadows.
-SDFGI can render together with depth-preoass.
-General fixes
-Added GPU detection
-Removed sync to draw, now everything syncs to draw by default.
-Fixed many validation layer errors.
-Added support for VkImageViewUsageCreateInfo to fix validation layer warnings.
-Texture, buffer, raster and compute functions now all allow spcifying which barriers will be used.
-When importing, a vertex-only version of the mesh is created.
-This version is used when rendering shadows, and improves performance by reducing bandwidth
-It's automatic, but can optionally be used by users, in case they want to make special versions of geometry for shadow casting.
-All shadow rendering is done with raster now (no compute)
-All shadow rendering is done by rendering directly to the shadow atlas
-Improved how buffer clearing is done to optimize the above.
-Ability to set shadows as 16 bits.
-SDFGI direct light is done over many frames
-SDFGI Changed settings for rays/frame
-SDFGI Misc optimizations
-SDFGI Bug fix on probe scroll
-GIProbe was not working, got it to work again
-GIProbe dynamic objects were not working, fixed
-Added a half size GI option.
