EZP-23397: Elasticsearch: Implement language filters

This PR resolves issue https://jira.ez.no/browse/EZP-23397

#### TODOs
- [ ] DRY refactor visitors changes
- [ ] \(post-review\) Create follow-up issue for field filters criteria test framework
Nothing is saying in this method that it will be set. Knowing that `getFieldFilter()` will set it is not sufficient IMHO.
Defensive approach :wink: