get rid of SoupSessionPrivate->conns hash
move cleanup/abort code from session to host
move some bits out of SoupMessageQueue
SoupAuthManager: simplify, don't depend on SoupMessageQueue

Rather than calling soup_session_get_queue() and getting the message's
connection via its' queue item, just call soup_message_get_connection().
drop soup_session_get_queue(), add soup_session_lookup_queue_item()
queue move wip