[PJRT] Remove the deprecated PjRtClient::LookupDevices() overload that takes a raw int.
[PJRT] Remove the deprecated PjRtClient::LookupDevices() overload that takes a raw int.

Update users to use the PjRtGlobalDeviceId overloads (or to use different APIs).

Fixes a TODO, no functional changes intended. However, the change is in preparation for allowing int64_t sized device IDs, so fixing up users of `int` device IDs is a preparatory step.
