Move entry_port_cfg_t fields in entry_connection_t

Move entry_port_cfg_t fields in entry_connection_t

Also rename some options for uniformity, and apply this script:

@@
entry_connection_t *conn;
@@
 conn->
+entry_cfg.
\(
 isolation_flags
\|
 session_group
\|
 socks_prefer_no_auth
\|
 ipv4_traffic
\|
 ipv6_traffic
\|
 prefer_ipv6
\|
 cache_ipv4_answers
\|
 cache_ipv6_answers
\|
 use_cached_ipv4_answers
\|
 use_cached_ipv6_answers
\|
 prefer_ipv6_virtaddr
\)