A number of headers in the codebase included `rendering_server.h` just for
some enum definitions. This means that any change to `rendering_server.h` or
one of its dependencies would trigger a massive incremental rebuild.
With this change, we decouple a number of classes from `rendering_server.h`,
greatly speeding up incremental rebuilds for that area.
On my machine, this reduces incremental compilation time after an edit of
`rendering_server.h` by 60s (from 2m57s).
- Implements asynchronous transfer queues from PR #87590.
- Adds ubershaders that can run with specialization constants specified as push constants.
- Pipelines with specialization constants can compile in the background.
- Added monitoring for pipeline compilations.
- Materials and shaders can now be created asynchronously on background threads.
- Meshes that are loaded on background threads can also compile pipelines as part of the loading process.
