Add unit tests for random_symbol_circuit_resolver_batch and random_circuit_resolver_batch

[mhucka]

Add unit tests to tensorflow_quantum/python/util_test.py to verify the output shapes and types of random_symbol_circuit_resolver_batch and random_circuit_resolver_batch.

[kenya-sk]

Hi @mhucka , I'm interested in this issue.
Can I handle this issue?

[mhucka]

@kenya-sk Thank you for your interest. I've assigned it to you.