Create an abstract `gss.Job` parent class

[bharat-thotakura]

What is happening?

With PR https://github.com/Infleqtion/client-superstaq/pull/691, cirq_superstaq/job.py and qiskit_superstaq/superstaq_job.py share a lot of common implementations. Motivated by Rich's comment, it would be useful to have a parent gss.Job class to factor out standard functionality in css & qss.

What are the current alternatives?

Update css and qss individually.

Any additional context?

No response