Our gossmap_store uncompresser generates nodeids with well-known
privkeys, so we can decrypt and respond to HTLCs sent to such nodes.
By replacing channeld with a fake, we can connect a node to another
node, but then once the channel is established, allow payments to be
sent into the generated network, and respond appropriately.
This minimal version handles MPP timeouts, but doesn't insert any
delays or runtime capacity for channels.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-None: Testing only
