[Python] types.py should have separate local and shared modules loops

[crwilcox]

PR googleapis/google-cloud-python#5364 shows the change we want. The generator is currently undoing this fix. The transform we are using right now is as follows:

replace(
    "google/cloud/*/types.py",
    "for module in \(\n(.*\n)*?\):\n(    .*\n)+",
    """_shared_modules = [
    http_pb2,
    iam_policy_pb2,
    policy_pb2,
    any_pb2,
    descriptor_pb2,
    duration_pb2,
    empty_pb2,
    field_mask_pb2,
    timestamp_pb2,
    status_pb2,
]

_local_modules = [
    cloudtasks_pb2,
    queue_pb2,
    target_pb2,
    task_pb2,
]

for module in _shared_modules:
    for name, message in get_messages(module).items():
        setattr(sys.modules[__name__], name, message)
        names.append(name)

for module in _local_modules:
    for name, message in get_messages(module).items():
    message.__module__ = 'google.cloud.tasks_v2beta2.types'
    setattr(sys.modules[__name__], name, message)
""")