Create queue for network events when channel is full

[austinabell]

Issue summary

Currently, if the channel is full, the event is ignored with an error log to avoid stalling the libp2p task:

forest/node/forest_libp2p/src/service.rs

Line 285 in 3411459

error!("network sender channel was full, ignoring event");

but it would be ideal to create some buffer (with something like VecDeque) when the channel is full to hold these pending events to send into the channel when the channel empties.

How the send from the queue is triggered can be done a few ways, but either just through a check at the start of the libp2p thread poll or as a future that is part of the select! are the ones that come to mind.

If this error is logged on other's ends we can also consider increasing the network event channel size (currently 50) to avoid this case, but I have yet to see the error log.

cc: @AshantiMutinta

Other information and links

[austinabell]

No need for this because will just use unbounded channels in #922