The copyright checker was allowing files with code above the copyright
line in a few places, mainly as a result of IDEs ordering imports
improperly.
This makes the check more robust, and adds a whitelist of valid lines
that may appear before the copyright line.
This runs our `js_unit_tests` and `node_unit_tests` in parallel, one
rust test per JS unit test file. Some of our JS tests don't like running
in parallel due to port requirements, so this also makes those use a
specific port-per-file. This does not attempt to make the node-compat
tests work.
