Added the ability to import scenes as AnimationLibrary
* Completes implementation of https://github.com/godotengine/godot-proposals/issues/4296
* Helps if you want to export animations to a separate file (say a GLTF) to avoid re-importing/exporting them every time the model changes.
* Helps if you simply want to have animations using a dummy model, which can be shared across multiple models.
Creates a secondary scene importer used only for animations.
**NOTE**: A new flag for scene importer: EditorSceneFormatImporter.IMPORT_DISCARD_MESHES_AND_MATERIALS has been added, to hint importers that they should skip meshes and animations (and hence make importing faster). It is not implemented in any importer yet, this should be done in a separate PR.
This makes it easier to spot syntax errors when editing the
class reference. The schema is referenced locally so validation
can still work offline.
Each class XML's schema conformance is also checked on GitHub Actions.
-Allows displaying custom options for specific file format variants
-Added support for scene format import to retrieve custom options
This PR is necessary for #54886 to be implemented properly.
* New plugin system to control the whole import workflow
* Can add options and run code at every import step (general, per node, mesh, animation, material etc.)
This constitutes a first version of these plugins. The ability to interact with the import preview dialog will likely be added later on.
