MINOR: cfgparse-listen: add and use cfg_parse_listen_match_option() helper

MINOR: cfgparse-listen: add and use cfg_parse_listen_match_option() helper

cfg_parse_listen_match_option() takes cfg_opt array as parameter, as well
current args, expected mode and cap bitfields.

It is expected to be used under cfg_parse_listen() function or similar.
Its goal is to remove code duplication around proxy->options and
proxy->options2 handling, since the same checks are performed for the
two. Also, this function could help to evaluate proxy options for
mode-specific proxies such as log-forward section for instance:
by giving the expected mode and capatiblity as input, the function
would only match compatible options.