webkitpy: merge message_broker.py into manager_worker_broker.py

webkitpy: merge message_broker.py into manager_worker_broker.py
https://bugs.webkit.org/show_bug.cgi?id=78999

Reviewed by Tony Chang.

This is pretty much a straight cut-and-paste of one file into
another (broken up so that docstrings and imports are in the
right place).

* Scripts/webkitpy/layout_tests/controllers/manager_worker_broker.py:
(BrokerClient):
(BrokerClient.is_done):
(BrokerClient.name):
(Broker):
(Broker.__init__):
(Broker.add_topic):
(Broker._get_queue_for_topic):
(Broker.post_message):
(Broker.run_message_loop):
(Broker.run_all_pending):
(Broker._run_loop):
(Broker._dispatch_message):
(_Message):
(_Message.loads):
(_Message.__init__):
(_Message.dumps):
(_Message.__repr__):
(BrokerConnection):
(BrokerConnection.__init__):
(BrokerConnection.run_message_loop):
(BrokerConnection.post_message):
(BrokerConnection.raise_exception):
* Scripts/webkitpy/layout_tests/controllers/message_broker.py: Removed.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108378 268f45cc-cd09-0410-ab3c-d52691b4dbfc