`AnimData`, NLA strips, and action constraints all have an
`action_slots` field in RNA. The purpose of this field is to list
the slots of the currently assigned action (if any) that are suitable
for the relevant ID.
However, this is not clear from the naming. In particular, given that
there is another field `action_slot` that represents the currently
assigned slot, the name `action_slots` could be easily misinterpreted
as a way to assign multiple slots at once, which is not possible.
To help clarify its actual purpose and meaning, this PR renames the
field to `action_suitable_slots`.
As a bonus, this also ends up decluttering the Python autocomplete when
looking for things related to `action_slot`.
Ref: #130892
Pull Request: https://projects.blender.org/blender/blender/pulls/130754
370a11342c