We're switching to the new terminology to avoid confusion in cases
where multiple jax processes are running on a single host, and each
process has a unique process_index/host_id.
This keeps aliases for the old `host_id` APIs for now, but these will
eventually be removed.
This was originally commited in
b77ef5138b631378e6a8ceb8bafc94fe91239bae, but reverted in
14acd070c2afb11c81fc91f43790577cd48cbf67 due to Google-internal test
failures from renaming the local_devices argument name. This change is
identical except it also adds staging for the argument name change.
9128ba0c74