style(dapi): better api for identities balances

[QuantumExplorer]

Issue being fixed or feature implemented

The previous API requires to pass a double structured list, this PR simplifies things.

What was done?

Changed the API to make it more friendly.

How Has This Been Tested?

Breaking Changes

Not breaking compared to previous version.

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have added "!" to the title and described breaking changes in the corresponding section if my code contains any
• I have made corresponding changes to the documentation if needed

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone