Improve the parsing of data urls in URLParser to bring it more up-to-
spec. At the moment, we cannot parse the components of the MIME type
since it is represented as a string, but the spec requires it to be
parsed as a "MIME type record".
Because non-ASCII code points have negative byte values, trimming away
control characters requires checking for negative bytes values.
This also adds a test case with a URL containing non-ASCII code points.
This adds more tests for AK::URL. Furthermore, this also changes some
tests to conform to what the reworked URL class does (and the URL
specification mostly expects).
