This might be up for debate, but for the purpose of copy/pasting
keyframes, I think including keyframes that only have a handle selected
is not what most users expect.
The more pressing issue of #139314 is probably already addressed with
!139349 (that one fixes cases where handles would be included in [box]
selection even though they are not visible), but handles -- e.g.
overshooting handles -- can easily get included in [box]selection
without the user actually wanting to copy/paste the whole keyframe.
This is now resolved by swapping the check for skipping a keyframe from
`BEZT_ISSEL_ANY` to `BEZT_ISSEL_IDX`.
Additionally, a bit of code was added so we can do the "early out" in
`copy_animedit_keys` under the same condition.
Pull Request: https://projects.blender.org/blender/blender/pulls/139352
5d7967fed8