url: reuse existing context in href setter

Correctness-wise, this removes side effects in the href setter if
parsing fails. Style-wise, this allows removing the parse() wrapper
function around C++ _parse().

Also fix an existing bug with whitespace trimming in C++ that was
previously circumvented by additionally trimming the input in
JavaScript.

Fixes: https://github.com/nodejs/node/issues/24345
Refs: https://github.com/nodejs/node/pull/24218#issuecomment-438476591

PR-URL: https://github.com/nodejs/node/pull/24495


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>