Ray support: is_initialized function

Description: Request Ray support for ray.is_initialize function. This is a helpful feature to check if Ray initialized properly. Example from Ray Docs:

import ray
ray.init()
assert ray.is_initialized()

ray.shutdown()
assert not ray.is_initialized()

Example use case from Charm4py examples/ray/simple.py

def main(args):
    ray.init()
    assert ray.is_initialized()

    ...

Output Message:

------------- Processor 0 Exiting: Called CmiAbort ------------
Reason: AttributeError: module 'charm4py.ray' has no attribute 'is_initialized'

charmplusplus / charm4py

Ray support: is_initialized function #262