Add suppport for SearchTemplateRequests

[sothawo]

Follow-up to #1725, there was a SearchTemplateRequestBuilder added to the NativeSearchQuery, but that is not the right place.

We need to define the parameters for a search template request and add a search(template) method to the different SearchOperations interfaces and implement them (#1725 only added the support the the ReactiveElasticsearchClient, not to the operations).

Note: update the answer in https://stackoverflow.com/questions/68572136/how-to-use-elastic-search-template-idstored-in-es-cluster-in-spring-boot-get-r when this is implemented

[sothawo]

falsely linked from PR #1894

[imchao9]

Has this finished now?
Hope can use this feature ASAP
If have some problem, I can help.

[sothawo]

This is still an open issue.