mx doesn't support `http_proxy`s requiring authorization (aka following the format `http://user:password@host:port`)

[zakkak]

mx appears to only support unauthorized http_proxys following the format http://host:port while it should also support http://user:password@host:port and set http.proxyUser and http.proxyPassword accordingly.

The code at fault is: https://github.com/graalvm/mx/blob/29c0debab406352df3af246be2f8973be5db69ae/mx.py#L12966-L12981

and https://github.com/graalvm/mx/blob/29c0debab406352df3af246be2f8973be5db69ae/mx.py#L13007-L13012