Adds tests for when the connection fails during
1) splice tx_signature
2) splice commitment_signed
Fleshed out the reestablish flow for these two cases and implemented the fixes to make these reestablish flows work.
Part of this work required changing commit process for splices: Now we send a single commit_part for the splice where previously we sent all commits, and accordingly, we no longer revoke in response.
Changelog-Fixed: Implemented splicing restart logic for tx_signature and commitment_signed. Splice commitments are reworked in a manner incompatible with the last version.
Added a test for splicing out that exposed some behavior and code glitches that are addressed in this commit.
Added test for splice gossip.
Also added documentation for how to do a splice out.
ChangeLog-Fixed: Added docs, testing, and some fixes related to splicing out, insufficent balance handling, and restarting during a splice.
Update the lightningd <-> channeld interface with lots of new commands to needed to facilitate spicing.
Implement the channeld splicing protocol leveraging the interactivetx protocol.
Implement lightningd’s channel_control to support channeld in its splicing efforts.
Changelog-Added: Added the features to enable splicing & resizing of active channels.
