Remember the output of failing (blacklisted) tests

* The raw outputs of failing tests are saved in the blacklist and if a
  test fails, and is expected to, will be used for comparison to track
  improvements and regressions.

* Comment in whitelist suggests that it should be used when our selser
  output is correct but failing due to limitations in the test setup.

* Reduce some code duplications in parserTests.js

* Also, some cleanup from when selser.changes.json was removed.

Bug: 50316
Bug: 51718
Change-Id: I46eab7ca7c4c58e43997abedcaa944a1e7c17064
Merge "Remember the output of failing (blacklisted) tests"