T88495: Part 1 of 2: Handle more templated <td>-attr scenarios

• Removed some artificial limitations in the handling of templated <td> attributes and simplified / documented the logic.

• Re-orged some if-then-else nests to make the code more readable.

• Testing:
  • The example in the bug report now parses and RTs correctly.
  • http://localhost:8000/_rt/enwiki/List_of_largest_container_ships now parses and renders properly.
  • Added a new test that captures the scenario seen in that page.

• The more complex scenario (which actually has a failing test in parserTests.txt) of multiple cells on the same line separated by || is not implemented yet. That will be part 2.

Change-Id: Ib4ad0a63b97463fbc3944d674945c12ead23f944