Update Portalbase to use with so close() isn't needed

[DJDevon3]

Portalbase hasn't received the same treatment that adafruit_requests has with Connection Manager using with and still requires explicit close() for most cases. Needs to have the adafruit_requests treatment for fetch and other functions so explicit close isn't necessary to remember. It would be nice to have Portalbase take care of closing the connection automatically after use. It could help with cutting down retries, failed connections, and crashes from too many sockets open.