Sync parserTests with core tests

* Failures on the newly added tests.
  - The table building test is a cosmetic whitespace failure
    which shouldn't matter.

  - The heading test seems to be because of differences in how
    entities are encoded in section anchor links. We have a bug/
    WIP patch for aligning this.

  - However, a selser failure for the heading test inadvertently
    exposed a serializer failure since we now see a mw:DiffMarker
    meta show up in serialized wikitext (that meta should never show
    up in wikitext!). "grep DiffMarker parserTests-blacklist.js"
    to see this. To be fixed in a separate patch.

Change-Id: I5bb892e74a57d346193c023a62f21419efdfa72e