Mint: Remember NUT-08 outputs in melt quote and reissue overspent lightning fees on startup check

[callebtc]

We should persist the NUT-08 outputs in the melt_quote db before attempting a lightning payment with pay_invoice so that an eventual later payment state check (for example in ledger._check_pending_proofs_and_melt_quotes) that turns out to be PAID can issue change and return that in a MeltQuoteResponse.

Right now we do not reissue overpaid fees if the melt quote is settled outside of the melt() method.