Replace olivere/elastic with official Elasticsearch Go client

[notque]

The codebase uses github.com/olivere/elastic/v7 which is outdated. The official Elasticsearch Go client would provide better support and performance.

[notque]

we are on Opensearch now, and the official ES go client will not work with opensearch. I have thus moved us to the official opensearch go client. that functions. I do now need to remove the previous deprecated client. but wanted to get everything working first.

#331

[notque]

it feels a bit slower a lot of times. I think it might be the connection strategy. going to test some variations. It's unreasonably slow often with the new lib.