[feature/session-storage] Major rename

 After a lot of work with the alternate session storage
 I have come to the realization that many of these functions
 are named incorrectly and have to be renamed to avoid confusion.

 The renames are:

     get -> get_session_and_user_data
     get_with_user_id -> get_session_and_user_data_with_id
     num_sessions -> num_active_sessions_for_user
     cleanup_expired_sessions -> cleanup_certain_expired_sessions
     cleanup_long_session_keys -> cleanup_session_keys
     get_user_ip_from_session -> get_user_data_and_ip_from_session
     get_newest_session -> get_user_data_and_newest_session
     get_user_online_time -> get_all_users_time_visibility

 PHPBB3-9733
 [feature/session-storage] Backport changes from alt-session-storage

 PHPBB3-9733