Add query for listing all tokens for a given Identity

[pshenmic]

Issue

On Platform Explorer, we want to show all identity's current token balances, which tokens and how much is the current balance of each

There is getIdentitiesTokenBalances query in the DAPI, but it requires you to pass a token id to get the balance. We don't know which tokens Identity have when we are opening the page, and we need a query to list all tokens by Identity

Feature request

Add a query for listing all tokens for a given identity, it should return you a token id together with current balance