xla

32da64f6 - [PJRT] Defer default device selection until we need to know the runtime (#4630)

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