Run Elasticsearch tests against multiple versions of Elasticsearch
After adding support for Elasticsearch V7 we will want our CI to run against V6 and V7 to prevent regressions. We already do the same thing for the indexer https://gitlab.com/gitlab-org/gitlab-elasticsearch-indexer but we should try and accomplish the same thing for all of the Rspec tests in GitLab which run against Elasticsearch.
We should be able to accomplish this by ensuring they are all tagged with :elasticsearch
so we know which ones we need to run against different versions.