Improve channel management endpoints

[fusion44]

The current channel handling implementation is very rudimentary. Improve the channel endpoints with the following features:

• [ ] Overview of the channel state (established, pendingOpen, pendingClose, pendingForceClose, waitingClose, ...)
• [ ] Update Wallet balance on state changes (ref #138)
• [ ] Send appropriate SSE messages when a state changes
• [x] Implement all the missing functionality for Core Lightning (channel balance distribution, remote node alias fetching, ...)
• ...

[fusion44]

Closed in favour for #199