Make TPU variable name deterministic.

Only use the unique variable handle id as handle cache key, but not the variable handle's name. This resolves a graph non-determinism issue seen in an internal workload. PiperOrigin-RevId: 435903760

Author: chuanhaozhuge

mesh_tensorflow/tpu_variables.py

@@ -82,7 +82,8 @@ def handle(self):
  if tpu_context is None:
  return self._primary_var.handle
 
- return tpu_context.get_replicated_var_handle(self._name, self._vars)
+ return tpu_context.get_replicated_var_handle(self._name, self._name,
+ self._vars)
 
  @contextlib.contextmanager
  def _assign_dependencies(self):