Fixed unhandled scenarios in the wikitext escaping <td> handler

* There was a missing check in the td-handler to see if the
  text-node was the first child of the <td> node since "-" in
  other children don't need escaping.

* Generalized fix from cc14d8b90 -- that patch only checked for
  <p> nodes that break td-content into multiple lines. This patch
  handles this more generally by checking if the text content
  being escaped is on the first line or on subsequent lines.

  Updated existing parser tests to capture this generalization
  (these tests would have failed without this fix). Marked one
  of these tests html2wt only since wt2html will not be able
  to match the html output being serialized.

* Updated and re-enabled a td-escaping (parsoid-only) parser test.
  The updated test would fail without this patch and passes with
  this patch.

* Applied the same fix to the existing li-handler which was missing
  the test for deleted node markers. The fix eliminates selser
  failures on an updated li-escaping test (which would have failed
  without this fix).

* Eliminates RT errors from fr:Manchester_City_Football_Club
  reported in bug 56918.

Bug: 56918

Change-Id: I5acd594eaa44e869a3f06b7365a16aaf6a94cfb7