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.
This was always the intent, but now we have to reconstruct from the
disparate fields.
This means `option_anchor_outputs` is now redundant.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Although it's deprecated already (because it stores as string), it's
better to make the name explicit. And create a new helper which stores as BIGINT.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
