Allow users to see current CTX on-chain fees (s/vb) and allow them to guide CTX on-chain fee rate.

[brianddk]

The LND wallet allows users to guide the fee choice on commitment transactions exchanged during lighting operations. The LND guidance is simple { low, medium, high }, but useful none the less. It would be useful to offer the same controls in Phoenix to request fee choices accordingly. In parity with this feature, it would be useful to show what the on-chain fee (s/vb) was used in the last exchange of commitment transactions, and a possible button to manually refresh commitment transactions in the event that the channel has been idle over a period of rapid fee escalation.

I think the Advanced options under channel management screen may have room for these controls, and seems a logical place.

[t-bast]

Hi, this isn't applicable anymore now that we're using anchor outputs and bitcoin support package relay. The fees of the commitment transaction can stay at 1 sat/byte and users don't have to think about it (and shouldn't have to think about it). We're even moving towards 0-fee commitments, which will improve this further (lightning/bolts#1228).