Update core and tango tests to match structure of epics tests

[coretl]

#714 rewrote the epics tests, improving the test matrix approach and adding some utils like MonitorQueue and ApproxTable to ophyd_async.testing. This ticket is to update the core and tango tests to use the same approach and utils.

Acceptance Criteria

• Core and tango tests use ophyd_async.testing.MonitorQueue and a similar style matrix approach.