TOP-891: Reset SUT before tests

This adds very basic reset logic to the SystemUnderTest to perform a full reset/initialization upon starting the test session, and to the SubarrayUnderTest to reset the subarray toObsState.EMPTY.

I made sure to run a pipeline where the SubarrayUnderTest.reset() functionality is actually used by leaving it in an IDLE state, here are the results for that run: https://ska-telescope.gitlab.io/-/ska-low-csp-test/-/jobs/5889186196/artifacts/build/baseline-test-integration/pytest-report.html. You can see in the test teardown that it calls the Abort command, followed by the Restart command, after which the CSP subarray has ObsState.EMPTY.