Update all DynamicsBackend code/tests to work with hex for meas level 2

[DanPuzzuoli]

Summary

Closes #375

Details and comments

A current issue I'm having with resolving all test cases is that the Result object, in a test like

test.dynamics.backend.test_dynamics_backend.TestDynamicsBackend.test_schedule_memory_slot_num

actually converts things back into integers (as strings) when calling get_counts.

[DanPuzzuoli]

To fix the tests I decided to directly look at the internal memory of the Result objects (through Result.to_dict()), which are stored in hex, and validate correctness. We can't control the behaviour the Result object, and at least this way we can validate the outputs of DynamicsBackend.