RequestList cannot be copied or moved, because m_pending_request_queue
contains lambdas that store pointers to the original RequestList and
completion steps that we don't have a reference to.
Fixes a bunch of WPT regressions and imports the ones that work.
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.
