Revamp tests with dummy license index

The tests in `scancode-results-analyzer` now depends on `check_json_scan` and `run_scan_click` from `scancode.cli_test_utils` to run scans and verify that license detection issues are bring caught, classified and reported properly.

But whenever license rules are added to the scancode rules, to solve these issues, these tests fail consequently and thus the test expectation files require regular updates when the scancode license rules are updated.

If we use a custom license index build-out of a handful of rules only, and use that in `run_scan_click`, then this could be solved.

1. Create a custom license index build-out of a handful of rules, for live scans.

2. Also, add files from the `timescale` repository (after changing from timescale -> some other name that won't be a license name ever), as tests for the summary and get_unique_license functions. https://github.com/nexB/scancode-toolkit/issues/2268

3. Create scripts to regenerate test expectations.

4. Add readme files for tests, how the test files were obtained.