- EditorSettings: Ensure that `create()` makes a valid singleton.
Fixes#49179, fixes#49450.
- EditorPaths: Cleanup code, properly set `paths_valid`.
- EditorPaths: Move more paths validation (check, mkdir) from
EditorSettings for a better separation of concerns.
- EditorPaths: Move EditorFileSystem creation of `.godot/imported`
next to other paths.
* Shader compilation is now cached. Subsequent loads take less than a millisecond.
* Improved game, editor and project manager startup time.
* Editor uses .godot/shader_cache to store shaders.
* Game uses user://shader_cache
* Project manager uses $config_dir/shader_cache
* Options to tweak shader caching in project settings.
* Editor path configuration moved from EditorSettings to new class, EditorPaths, so it can be available early on (before shaders are compiled).
* Reworked ShaderCompilerRD to ensure deterministic shader code creation (else shader may change and cache will be invalidated).
* Added shader compression with SMOLV: https://github.com/aras-p/smol-v
