[Enhancement] Add inbound and outbound fee rates in channel overview

[hieblmi]

Displaying channel fees(especially fee-rate in ppm) helps routing node operators to more efficiently take decisions on manual fee rate adjustments.

Proposed below are four new column headers BASE_FEE_IN, BASE_FEE_OUT, IN-FEE(ppm) and OUT-FEE(ppm) that would display incoming and outgoing fee rates in ppm satoshis.

[ Channels ]                                                                                                                   [ Wallet ]
 balance: 1000 (1000|0)                                                                                       balance: 500 (500|0)
 state  : 10 active 0 pending 0 inactive
 gauge  : [|||||||||||||||     ] 75%

STATUS        ALIAS        BASE_FEE_IN IN-FEE(ppm)    BASE_FEE_OUT     OUT-FEE(ppm)         GAUGE                 LOCAL          CAP         SENT     RECEIVED  HTLC UNSETTLED  CFEE   LAST UPDATE     PRIVATE ID         

[edouardparis]

closed by #72 🎉