The versioning code that upgrades legacy actions to new slotted actions
also needs to properly assign slots to the IDs that use those upgraded
actions. It was doing this correctly except for not traversing into and
assigning slots to embedded IDs.
This commit adds the code to handle embedded IDs as well.
Additionally, this changes how mismatched `id_type`s are handled when upgrading
actions. Rather than refusing to assign the slot created during the upgrade if
the `id_type` doesn't match the ID, we assign it anyway with a warning. The
rationale is that this represents a case where the Action `idroot` was already
mismatched, and it turns out that has always been possible. So we now opt to
simply preserve that state of affairs rather than attempt to "fix" it.
Pull Request: https://projects.blender.org/blender/blender/pulls/129002
989634c0a1