Change order of precedence of whitelist and blacklist for pattern filtering

[zippolyte]

What does this PR do?

The order is now: apply whitelist, then apply blacklist on remaining set of elements

Motivation

The other way is really counter intuitive and confusing. For example, if you blacklist a single element, that doesn't appear in your original set, then no matter what you set as a whitelist, the filter will always return your entire set.
This can appear as a bug, but technically it is not since the metrics you whitelisted are here all right, and the ones you blacklisted aren't.
This should answer #1527 (comment)

Review checklist

• PR has a meaningful title or PR has the no-changelog label attached
• Feature or bugfix has tests
• Git history is clean
• If PR impacts documentation, docs team has been notified or an issue has been opened on the documentation repo

Additional Notes

Anything else we should know when reviewing?

[codecov-io]

Codecov Report

Merging #2174 into master will decrease coverage by 12.05%.
The diff coverage is 90%.

[ofek]

Excellent!