Wipe `get_claimable_balances` for timed-out, closed, inbound channels, with 0 balance

[TheBlueMatt]

If we have an inbound channel where funding timed out and we have zero balance, the monitor can be deleted, so get_claimable_balances should return an empty set.

[shaavan]

Would love to take a look into this!

[jbesraa]

hey @shaavan
are you still interested in doing this?

[shaavan]

Hi @jbesraa!

I got involved with some other commitments and couldn’t find time to work on this properly! Feel free to take this up, if you’d like! :)