[gnokey] Query balance of a realm

[leohhhn]

Description

We should add a way to check the balance of a realm via gnokey query. The only way to check a realms balance is to somehow get its address and check either with bank/balances or via Gno code.

I propose an extension to the bank/balances query that will be able to also take in a path, for which it will automatically derive an address to check the balance of. Should be a pretty simple addition.

cc @deelawn