Align FakeJob with the methods of the RuntimeJob

[wshanks]

This is good for now. I noticed our FakeJob is implemented differently from the removed FakeJob and also from current Jobs. For example, the qiskit-ibm-runtime Job doesn't have time_per_step() implemented currently. If we're using our own FakeJob going forward, we should make sure it matches the external specs.

Originally posted by @coruscating in #1384 (comment)