Major cleanup based on test reviews I was doing as part of #31804
I've tried to keep the tests as similar as I can (although I'm very unsure why we're testing some of the protected methods). But the main aim is to reduce the amount of image instances we are creating unnecessarily and remove dependencies on the ImageInspector. There are two instances left in tests directly related to test the filter function which I still need to figure out but will be PR'd independently of this
Testing
Testing is purely on code review + Drone passing as this is only touching the tests