No functional changes
The keying set code was passing around a list
of `tRKS_DSource` through a lot of functions.
It turns it this was just a ListBase wrapper around `PointerRNA`.
So to make it clearer what is passed around, I replaced the
`ListBase` with a `Vector<PointerRNA>`
To make the use of `ANIM_relative_keyingset_add_source` clearer
I made two functions out of it with different parameters.
Those can take the vector as a reference and
EITHER only an `ID *`
OR an `ID *`, `StructRNA *` and a `void *`
Pull Request: https://projects.blender.org/blender/blender/pulls/113675
b753ef73a0