Quality gate should use expected_namespaces to filter results

[wagoodman]

Today we filter the results of the grype scans down to what namespaces are in the subject database. A more robust way to do this would be to filter down to what is expected (which is available in the config.yaml file for each provider). Additionally this would allow for a narrower measure of what is under test. Today it's not as ideal since the github provider needs to have alpine results be accurate, however, we only need to measure language-specific results... which means we are not as sensitive as we could be to possible changes to the specific providers under test, which is not great.