[recovery]: try to CPFP anchor for restored channel

[guggero]

Background

Currently if a channel is restored using SCB we don't look at the mempool to figure out if there already is a commitment transaction published by the remote side, lnd just sits there and waits for a commitment transaction to confirm.
This assumes that the remote party will eventually CPFP their anchor to get the transaction confirmed.
But if the channel doesn't have any balance on the remote side, then they can't do it and the commitment TX will be stuck in the mempool if it doesn't have enough fees.

There is a workaround available now with chantools pullanchor (PR here: lightninglabs/chantools#100), but it would be great if we could inspect the mempool and attempt to sweep our anchor even if we restore a channel from SCB.

Steps to reproduce

1. Open anchor channel, don't send any payments
2. Reset funder node, restore channel from SCB
3. Observe peer force closing but not pulling the anchor because they have no balance
4. Channel just sits there