Support search_type in Rank Evaluation API #48503
Description
The Rank Evaluation API could benefit from adding support for the search_type query string parameters.
I have a (small) set of identical documents that would score equally when using search_type=dfs_query_then_fetch but be "very" different when not.
This could impact the ranking and therefore the metric score as well. So when comparing different approaches to queries / analyzers it is hard to tell whether the differences in metric scores is caused by the different approaches or where the documents are stored.
One workaround is to ensure there is only 1 node, 1 shard and 0 replicas in your test setup.