Interop testing with Eclair revealed an issue with remote funding key rotation.

This searches for the funding output using the rotated remote funding pubkey instead of the furrent funding pubkey.

Also update the variable name to be more clear which this represents.

Changelog-Changed: Interop fixes for compatability with Eclair

This is needed to remember if a splice was locked and reconnect occurs mid `splice_locked` attempted so it can be resumed in reestablish.

This field should be serialized for communication between channeld and lightningd.

To support resuming `splice_locked` across channel reconnect, we need to pass inflight `is_locked` between lightningd and channeld.

This implements that interface between channeld and lightningd so each inflight should have up to date `is_locked` values between restarts.

Use the inflight information to set a correct `locked_txid` value on restart. This is critical for handling interrupted `splice_locked` events that need to be resumed on reconnect/reestablish.

A new case where `splice_locked` must be sent again on reestablish.

This handles the case where `splice_locked` did not complete locally or remotely and must be resumed.

The interaction betwen libwally and CLN’s memory management is tricky. Let’s dodge that problem and just clone the PSBTs.

Clean up some unused PSBT / ictx code while we’re at it

Upscale user provided PSBTs to v2 and convert them back to user preference when returned.

Check that the peer sent the correct txid in their `splice_locked` message.

We have to check this later on in `check_mutal_splice_locked` so we store the value in `splice_state`