Add adapter for calling Elasticsearch/OpenSearch using Gitlab::HTTP

In ee/lib/gitlab/search/client.rb we have one adapter which calls ::Gitlab::Elastic::Helper.default.client and delegates methods. We want to move away from the gem and instead use Gitlab::HTTP.

Create a new adapter that uses Gitlab::HTTP and connects to Elasticsearch/OpenSearch. OpenSearch could use Aws::Credentials to authenticate.

At the start, this adapter won't be called.