Drop ChannelMonitors for inbound, no-local-funding channels after they time out

[TheBlueMatt]

We continually have issues where users have channels that were never funded (the funding transaction never confirmed/was conflicted) and because we don't see the channel close, we never allow the ChannelMonitors to be pruned, leaving a Balance::ClaimableOnChannelClose lying around forever. Properly pruning these channels for channels where we contributed some funds (either because the channel was outbound-v1, we received some push_msats for inbound-v1, or a dual-funded v2) takes tracking the inputs for the funding tx and actually detecting a conflict which makes funding lock-in impossible, but we could at least do the trivial case where we don't have any funds to recover and the channel has timed out so we FC'd it anyway.

[TheBlueMatt]

Optimistically tagging 0.1 in the hopes someone finds the time to pick it up (and it shows up as important), but if it doesn't make it so be it and we can move it to a friday issue.