Unify names of our mpsc channels

[leviathanbeak]

While #492 has not yet been merged, in it we use rx and tx prefixes when naming our Sender and Receiver channels.
An example would be rx_request_event.

In other modules, channel names do not follow that convention, even worse (imo) they are too vague as:
sender, broadcast, receive etc

I would like us to have more meaningful and unified channel names.
I propose rx/tx prefixes + descriptive name, but I am open to other ideas as well.

[Dentosal]

This is otherwise nice, but unfortunately tx is used for transaction in many contexts, which might be confusing.

[Voxelot]

closing as the channels have been largely removed during the architecture migration