When the XML parser appends child nodes to a template element, it must
actually append the template element's contents. This special behavior
caused us to return to the wrong parent element after adding child
nodes to a template element, leading to a crash.
When constructing an entry list, XHR::FormDataEntry is created
manually and appended to the entry list instead of using the
spec-defined method of creating an entry.
This allows us to disable test output, which performs expensive assert
tracking. This was making our imported tests run significantly slower
than tests run via `WPT.sh`.
Formatting the output ourselves also allows us to remove unnecessary
information from the test output.
This commit also rebaselines all existing imported WPT tests to follow
the new format.
