[PJRT] Cherry pick local rank changes to r2.0 release (#4712)
* [PJRT] Change the name of `LOCAL_RANK` to fix conflicts (#4646)
* [PJRT] Change the name of `LOCAL_RANK` to fix conflicts
* formatting
* Update usage of local rank in GPU config
* [PJRT] Use the new local rank env var to calculate local_ordinal (#4684)
* Use the new local rank env var to calculate local_ordinal
* formatting
* [PJRT] Remove start method from _run_singleprocess (#4709)
