feat: query many identity balances at a time

[QuantumExplorer]

Issue being fixed or feature implemented

For issue #2113

Right now you can only query one identity balance at a time, which is not efficient.

What was done?

Added a query allowing users to query many identity balances at a time.

How Has This Been Tested?

Not yet tested, should be tested in QA.

Breaking Changes

Not breaking.

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