When we sent out an HTLC-Timeout or HTLC-Success tx, we need to spend
it after the timeout so it's safely in our wallet.
We generalize the tx_type OUR_UNILATERAL_TO_US_RETURN_TO_WALLET to
OUR_DELAYED_RETURN_TO_WALLET, since we use it for HTLC transactions too.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
When we see an offered HTLC onchain, we need to use the preimage if we
know it. So we dump all the known HTLC preimages at startup, and send
new ones as we discover them.
This doesn't cover preimages we know because we're the final
recipient; that can happen if an HTLC hasn't been irrevocably
committed yet. We'll do that in a followup patch.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>