With this change we no longer stretch "width: auto" for replaced
elements and also use "width calculation rules for block-level replaced
elements", like suggested by the spec.
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.
