[FEATURE] API for fetching async search status

[eirsep]

Customers running search requests with large response size(due to results or doc size) want to be able to track the status of their search.
The get async search by id API provides the entire response which may be too large if customer simply wants to check the status of the search

We can have a dedicated status API to shed light on the status of an async search which has a light weight response showing state, creation time and other details such as shards left to query, query/fetch phase, agggregations etc.( if search is still in progress )