add optional confirmation_height_frontier to get_nft_owner_assets

[ghost]

https://docs.nano.org/commands/rpc-protocol/#account_info

the call to get_nft_owner_assets can be sped up if we can pass in a confirmation_height_frontier rather than calling account_info every time get_nft_owner_assets is called.

we have to get confirmation_height_frontier to make sure that the owner didn't change but if the client already knows the owner didn't change, and knows the previous confirmation_height_frontier, they can get the data faster by providing this value as input.

This would speed up the api calls on NFTS that we know didn't change ownership because we own the nfts and didn't send them anywhere.

unfortunately, banano isn't up to v22 yet so include_confirmed does nothing