The goal here is to avoid having to cast to and from `ID` when getting the
evaluated or original ID using the depsgraph API, which is often verbose and not
type safe. To solve this, there are now `DEG_get_original` and
`DEG_get_evaluated` methods which are templated on the type and use a new
`is_ID_v` static type check to make sure it's only used with valid types.
This allows removing quite some verbosity on all the call sites. I also removed
`DEG_get_original_object`, because that does not have to be a special case
anymore.
Pull Request: https://projects.blender.org/blender/blender/pulls/137629
f442c86197