If we expect further events for an onchain output (because we can steal
it away from the 'external'/rightful owner), we mark them.
This prevents us from marking a channel as 'onchain-resolved' before
all events that we're interested in have actually hit the chain.
Case that this matters:
Peer publishes a (cheating) unilateral close and a timeout htlc (which
we can steal).
We then steal the timeout htlc.
W/o the stealable flag, we'd have marked the channel as resolved when
the peer published the timeout htlc, which is incorrect as we're still
waiting for the resolution of that timeout htlc (b/c we *can* steal it).
Any file in this directory which is executable and whose name only
consists of alphanumeric characters, space, '.', '-' or '_' will be
automatically loaded when lightningd starts (unless suppressed with
commandline options).