Mnnvl with split comm

[chuangz0]

support split comm and get_local_mnnvl_comm

split_comm

def split_communicator(comm: WholeMemoryCommunicator, color: int, key: int = 0):
    """Split Communicator.
    Creates a set of new communicators from an existing one. Ranks which pass the same color value will be part of the
    same group; color must be a non-negative value.
    The value of key will determine the rank order, and the smaller key means the smaller rank in new communicator.
    If keys are equal between ranks, then the rank in the original communicator will be used to order ranks.
    """

[linhu-nv]

Seems good to me.

[BradReesWork]

/merge