Now that Array.prototype.join() is producing the correct results we
can remove the separate code path for arrays in Value::to_number()
and treat them like all other objects - using to_primitive() with
number as the preferred type and then calling to_number() on the
result.
This is how the spec descibes it.
This also means we don't crash anymore when trying to coerce
[<empty>] to a number - it now does the following:
[<empty>] - to string - "" - to number - 0
[<empty>, <empty>] - to string - "," - to number - NaN
The addition of assert functions to Userland/js
was done before we had load(..) implemented. Now
that it exists, it seems like the right move the
test helper functions to pure javascript instead
of poluting js with random global functions.
