These methods return a list of channels that can be rebalanced,
in order to receive or send a given amount.
Also add 'channels' parameter to submarine swaps.
Previously, swaps were not considering which channel to use.
When we do not have liquidity to pay an invoice:
- add 'rebalance' option in order to pay an invoice
- use the suggested channel in the 'swap' option
When we do not have the liquidity to receive an invoice:
- add 'Rebalance' and 'Swap' buttons to the receive tab