Add fee bumping functionality

[hsjoberg]

No description provided.

[hsjoberg]

Related PR #1319

[Darth-Coin]

Please add a functionality to bump the fee for force closed channels.
I have a FC for 2 months pending and can't do anything.

I had a channel with Coingate, working just fine.
Then I sent few sats to a zeuspay LN address (hold invoice).
In my Blixt appeared as "open".
The receiver confirmed that was received in his Zeus node.
I even kept my Blixt in persistent mode for many hours.
After 5 days, I reopen my Blixt and the channel with Coingate, through which that hold invoice was paid, got force closed. And seems to be triggered from my side, not from Coingate side.
The FC was sent with a 10sat/vB and got stuck in mempool without any option to bump the fee.

For weeks I just re-broadcast the tx using mempool and https://bitaccelerate.com, just to keep it "alive" in the mempool and not be kicked out.

Then I deposited 100k sats to Blixt onchain, hoping that will be re-broadcast with a higher fee from that new UTXO.
It doesn't. Seems that force close channels cannot be bumped with a higher fee automatically.

Please add a functionality like Zeus have, to bump the fee manually for a pending tx.