Create plan to automate kibana-docker settings

[jbudz]

kibana-docker contains an allowlist of kibana.yml settings used to know which available environment variables are meant for kibana. This list is updated manually and can become out of date.

[elasticmachine]

Pinging @elastic/kibana-operations

[tylersmalley]

Long term would be to do what ES does and use any ENV with a period and whitelist those without a period. To do this we need to move away from camel-cased config settings, which we have wanted to do for a long time.

For now, we should be able to fetch the docker settings and populate the entry file.

[tylersmalley]

Unfortunately, this is not something we can prioritize in the foreseeable future.