Expose features option in Get Index API #82948
Description
The Get Index Api always fetches all mappings, aliases and settings for each index it return results for.
It is possible to filter unwanted information out by using filter_path option, but this only avoids the unneeded
to be added to the response. The information is still computed on the Elasticsearch side. Especially getting
the mappings is relatively expensive here, since this requires uncompressing certain parts of the cluster state.
Internally the Get Index Api has a functionality called features that allow certain parts of an index not be computed / fetch to begin with. Unfortunately this option isn't exposed in the rest layer. We should expose this feature to avoid Elasticsearch from doing unnecessary computations for things that the caller of the get index api will not use anyway.