Auto-configure Elasticsearch REST client in Spring Data

[bclozel]

As described in #15008, Spring Boot already auto-configures a RestHighLevelClient bean, and it should reuse that bean in an auto-configuration to create an ElasticsearchOperations component when Spring Data Elasticsearch is available.

See AbstractElasticsearchConfiguration in Spring Data Elasticsearch.

[bclozel]

Created DATAES-563 while working on this.