block/nfs: Use URI parsing code from glib

block/nfs: Use URI parsing code from glib

Since version 2.66, glib has useful URI parsing functions, too.
Use those instead of the QEMU-internal ones to be finally able
to get rid of the latter.

While we're at it, slightly rephrase one of the error messages:
Use "Invalid value..." instead of "Illegal value..." since the
latter rather sounds like the users were breaking a law here.

Reviewed-by: Eric Blake <eblake@redhat.com>
Message-ID: <20240418101056.302103-12-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>