xla

a4a47369 - [PJRT] Defer default device selection until we need to know the runtime (#4630) (#4640)

[PJRT] Defer default device selection until we need to know the runtime (#4630) (#4640) * Defer default device selection until we need to know the runtime * formatting * More formatting * Reimplement in python * Revert C++ changes * Use xenv variable * Add to configuration.yaml * add xla_dist test case * formatting