Provide option to set tx fees

[ObjectiveTester]

Description

Povide an option to set tx fees

Steps to reproduce the behavior

When initially funding, I set a tx with less than 10sat/byte which (after confirming) was sent on by the app at over 90sat/byte - this 2nd transaction was over 5% of the amount I funded the app with

Please provide a UI option to set tx fees manually and/or match the fee level for the initial transaction

[brianddk]

@ObjectiveTester to channel initiators have the ability to set the closing transaction fee? I'm unclear as to how much latitude the initiator has after reading BOLT003.

Also curious about what happens when the market fee rate grows beyond the channel reserve while the channel is still open.

In either case, the opening TXN should be 100% settable and the closing TXN should at least have a fee goal that is negotiated against (assuming I'm reading this right).