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.
Regardless of what the shorthand property is, if all its longhands are
the same CSS-wide keyword such as "initial" or "inherit", then it's the
same as the shorthand being that value.
This gets us 2 WPT subtest passes.
