Use TokenStreamPatcher to convert table tags outside wikitables to text

* Keep track of table nesting in token stream patcher and use it to
  convert <td>, <tr>, and <th> tags to plain strings.

* Fixes 24 (wt2html,wt2wt,html2html,selser) tests and improves
  results of 5 previously blacklisted tests. The failing selser
  test is actually a false failure because selser is more accurate
  than non-selser wts.

* Consolidated a few separate tests into a single test that covers
  all this functionality.
  - This new test fails wt2wt and html2wt modes because serializer
    uses tokenizer information which continues to return table tokens
	and results in <nowiki> wrappers.

Bug: 66489
Bug: 66498
Change-Id: I06d761acac4990d22bbd7b6c1f13c82284b2d044