Expand the `AnimData` struct with an `Animation *` + an
`binding_stable_index` field, and properly handle those relations.
This also adds functionality for actually pointing animated IDs to
`Animation` data-blocks, and automatically hooking up the relevant
`Binding`.
The Depsgraph code is extended to take these new relations into account,
but doesn't trigger any animation evaluation yet.
For more info, see #113594.
Pull Request: https://projects.blender.org/blender/blender/pulls/118677
Add code (including RNA wrappers) for:
- Creating, removing, and accessing `Animation` data-blocks.
- Creating and removing layers, strips, and bindings on those `Animation`
data-blocks.
- Accessing those via RNA.
Note that this does not include assignment to any animated data-block,
so it is of limited practical use.
For more info, see #113594.
Pull Request: https://projects.blender.org/blender/blender/pulls/118677
