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
`getFieldFilter()` will always return `null` or a valid filter, and if `$fieldFilter` is not `null` it is used as a whole only. What is accessed and modified is `$filter`, not `$fieldFilter`.