Add minimal support for the `Animation` data-block to the anim filtering
code. This means:
- F-Curves in the `Animation` data-block are shown in the Dope Sheet and
Graph Editor.
- The `Animation` is shown underneath each animated data-block, just
like an `Action` would be.
- Contrary to Actions, the expanded/collapsed state is stored on
`id->adt` and not on `Animation`. Because an `Animation` is intended
to be used by multiple data-blocks, they each should have their own
flag for this.
- In the filtering code, this PR adds the 'fillanim' channel type. This
is simply mimicking the name from the Action's 'fillact' type.
Limitations:
- Deleting of F-Curves is explicitly blocked, as that'll be introduced
in a later PR. The block prevents Blender from crashing.
- The Dope Sheet doesn't have an Animation mode yet, that'll be for a
later PR too.
Pull Request: https://projects.blender.org/blender/blender/pulls/120654
933f74ca02