[Stable plugin api] Add a default parameter to ListSetting 

### Description

ListSetting does not allow to define a default parameter at the moment, and it would be convenient to have this
@ListSetting(path="xxx", defaultValue=["1"])
List<String> list();
However Lists of custom types might not be easy with this parameter
follow up from a review:
https://github.com/elastic/elasticsearch/pull/92334#discussion_r1065843783