Before
1. prepare-frontend
2. prepare-backend
3. build-static-viz
4. files-changed-check
5. static-viz-files-changed-check

So, we're doing all these expensive operations before the step 4, even though they might not even be necessary.
If files changed already outputs backend_all, this means we have to run these tests whether or not there were static-viz changes.

After
1. test which files changed
    - if backend_all output -> skip static-viz-bundle and start running tests straight away
    - else if there are no direct backend changes, have an additional check for static-viz
2. static-viz-files-changed
    - if true -> run tests
    - else -> skip tests