gh-94518: Rename `group*` to `extra_group*` to avoid confusion by arhadthedev · Pull Request #101054 · python/cpython

This PR addresses #94687 (comment):

Todo: replace groups_size/groups parameter names with extra_group_size/extra_groups across the whole file to avoid confusion of passers-by. It's necessary to mitigate a misleading name of setgroups that supposes replacement of not supplimentary group affinities, but all ones. The mislead results in seeing the omission of setgroups call for groups_size == 0 as a bug (like we should reset the inherited affinities but do nothing instead).

I'll do it in a separate PR because both this PR and gh-94519 are already big enough to clobber them with extra details.

Edit: this PR also unifies terminology by further renaming groups_list parameter and num_groups variable into extra_groups_packed and extra_group_size.

cc @gpshead

• Issue: Port 23-argument _posixsubprocess.fork_exec to Argument Clinic #94518