Resolve Naming of Inconsistent "Config" Options

Description of issue: the "`CONFIG PATH`" long option is "`--path.config`" whereas all other "CONFIG" options are "`--config.$option`". The consistency of prepending configuration with "`--config`" was what I had expected.
Expected State: `--config.path`
Current State: `--path.config`

Version: logstash-5.6.3-1.noarch
Operating System: tested on Centos/7
Config File (if you have sensitive info, please remove it):
Steps to Reproduce: Run `/usr/share/logstash/bin/logstash --help`

Start at the `/usr/share/logstash/bin/logstash` entry point and run `logstash --help` to inspect how the CONFIG options are exposed. Trace the option definition responsible for `--path.config`, then confirm that the help output uses `--config.path` consistently with the other CONFIG options.

Written by the indexing model from the issue text.