Add agent communication wrapper.

[Gamenot]

Still WIP.

See #1839 for context.

New plan

Message format is like:

class Header(NamedTuple):
   channel: str
   sender: str
   sender_type: str
   cc: Set[str]
   bcc: Set[str]
   format: str

class Message(NamedTuple):
   content: Any

Use idea is the following:

def filter_useless(transmissions):
   for header, msg in transmissions:
      if header.sender in ("parked_agent", "broken_stoplight"):
         continue
      if header.sender_type in ("advertisement",):
         continue
      yield header, msg

class GossiperAgent:
   def __init__(self, id_, filter, friends):
      self._filter = filter
      self._id = id_
      self._friends = friends

   def act(self, observation):
      out_transmissions = []
      for header, msg in filter(observation["transmissions"]):
         if not {self._id, "__all__"}.intersection(header["cc"] | header["bcc"]):
            continue
         if header.channel == "position_request":
            out_transmissions.append((
               Header(
                  channel="position",
                  sender=self._id,
                  sender_type="ad_vehicle",
                  cc={header.sender},
                  bcc={*self.friends},
                  format="position",
               )._as_dict(), # optimize this later
               Message(
                  content=obs.ego_vehicle_state.position,
               )._as_dict(), # optimize this later
            ))
         ...
      ...
      action = policy.select_action(observation)
      return (base_action, out_transmissions)

# for now
env = MessagePasser(
   hiwayv1env,
   max_message_bytes=MESSAGE_BYTES,
   message_config={
      "gossiper0": (
         V2XTransmitter(bands=Bands.ALL, range=100, available_channels=["position_request", "position"]),
         V2XReceiver(bands=Bands.ALL, aliases=["tim"], blacklist_channels=["self_control"]),
      ),
      ...
   },
)
gossiper_agent = GossiperAgent("gossiper0", filter=filter_useless, friends={"schemer", "gossiper1"})
oblivious_gossiper_agent = GossiperAgent("gossiper1", filter=filter_all, friends={"schemer"})
schemer_agent = SchemerAgent("schemer")

# then just the standard gym interface with no modifications
obs, info = env.reset()
for ...:
   actions = {agent_id: agent.act(obs[agent_id]) for agent_id, agent in agents}
   obs, reward, term, trunc, info = env.step(actions)