Use own implementation of date formatters.

[sothawo]

Currently the ElasticsearchDateConverter has a dependency on org.elasticsearch.common.time.DateFormatter and org.elasticsearch.common.time.DateFormatter to convert Java classes to and from the different date formats that Elasticsearch supports.

These classes live in the core Elasticsearch library and not in one of the client libraries. To not risk licensing issues when ES changes it's license with 7.11, the formatting code must be implemented from scratch in Spring Data Elasticsearch.