Add Fields option to the datasource or at the query editor to select only few fields

[Thamizhvanan-R]

Is your feature request related to a problem? Please describe.
The opensearch lucene query allows to query the data but we don't get an option to select only certain fields from the result. Often we need to show only certain fields from the data but fetching whole data puts load on the network.

Describe the solution you'd like
An option to include/exclude certain fields from the result either in the datasource configuration page or in the query editor.

Describe alternatives you've considered
We can use transform functions to drop the fields at the grafana, but fetching all the fields from the opensearch puts load on the network and memory.

Additional context
Add any other context or screenshots about the feature request here.

[kevinwcyu]

I'll be moving this to our backlog for further investigation and prioritization. This can potentially be done with https://opensearch.org/docs/latest/api-reference/common-parameters/#filtered-responses.