Finally.. i've been meaning todo this for ages since the
actor-id-swap-as-handshake is better layered as part of the IPC msg-ing
machinery and then let's us encapsulate the connection-time-assignment
of a remote peer's `Aid` as a new `Channel.aid: Aid`. For now we
continue to offer the `.uid: tuple[str, str]` attr (by delegating to the
`.uid` field) since there's still a few things relying on it in the
runtime and ctx layers
Nice bonuses from this,
- it's very easy to get the peer's `Aid.pid: int` from anywhere in an
IPC ctx by just reading it from the chan.
- we aren't saving more then the wire struct-msg received.
Also add deprecation warnings around usage to get us moving on porting
the rest of consuming runtime code to the new attr!
c85606075d