Add support for a specific deprecation logging that can be used to turn
on in order to notify users of a specific feature, flag, setting,
parameter, ... being deprecated.
The deprecation logger logs with a "deprecation." prefix logge
(or "org.elasticsearch.deprecation." if full name is used), and outputs
the logging to a dedicated deprecation log file.
Deprecation logging are logged under the DEBUG category. The idea is not to
enabled them by default (under WARN or ERROR) when running embedded in
another application.
By default they are turned off (INFO), in order to turn it on, the
"deprecation" category need to be set to DEBUG. This can be set in the
logging file or using the cluster update settings API, see the documentation
Closes#11033
045f01c085