add itests covering transport-connection interruption and reconnection logic

[dstadulis]

Description

When Pool's auctioneer or various subservices that interact with Pool client are restarted, trading clients often times have a don't reconnect well to the Auctioneer

Pool's main state machine should
[] properly wrap all errors [how]
[] Inspection if it was a connection issue/interruption
[] Pass connection interruption events to the reconnection logic

Action Items:
[] Add itest to validate all connection termination events are properly handled by Pool.

Shaping

Check what kind of error is returned when Aperture is killed?
- Is it a wrapped error?
Cannot be decoded because it’s just a string
Only works if it’s an error struct
Prob easy to test with setup appt kill and observe the error

https://github.com/lightninglabs/pool/blob/master/auctioneer/client.go#L1049

UX expectations

As long as the Auctioneer and the Client are running and connected to the network, they will eventually reconnect regardless of previous connection fluctuations.