Add missing features for SearchRequest

[prafsoni]

The following features are missing from the search request.

• [x] Support for multiple Sort
• [x] Source filtering
• [x] Stored Fields
• [x] Scripted Fields
• [x] track_scores supports
• [x] Doc Value Fields
• [x] post_filter
• [x] highlighting
• [x] Rescoring
• [x] Search Type
• [x] Scroll
• [x] Preference
• [x] version
• [x] seq_no_primary_term
• [x] indices_boost
• [x] Named Query (Added support to include matched_queries in response. However, Setting _name for query is a change in supported Queries)
• [x] inner_hits
• [x] Field collapsing
• [x] search after

https://www.elastic.co/guide/en/elasticsearch/reference/6.8/search-request-body.html

[prafsoni]

19128ae5b2ce537a1132c0347e6dffddfd557a9d