getwalletpakinfo should return the full pak entry

right now it doesn't, meaning if you don't save `initpegoutwallet` data you may have to call it again with the correct args to get it back

current work-around is to just call it again with same xpub/descriptor, and same `liquid_pak` pubkey.

Start by locating the getwalletpakinfo entry point and the related initpegoutwallet handling. Compare the returned data with the stored PAK entry; done means getwalletpakinfo returns the full entry so callers do not need to repeat initpegoutwallet with the same xpub, descriptor, and liquid_pak public key.

Written by the indexing model from the issue text.