[Elasticsearch] schema versions table
A continuation of https://gitlab.com/gitlab-org/gitlab-ee/issues/328
After converting ActiveModel related search modules in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14428, we need to create database table to store a list of schema versions. A rough proposal would be the following:
- friendly name
- index_name (e.g. "gitlab-development-V12p1")
- url
- aws region
- aws access key
- aws secret key
- version (e.g. 'V12p1')
- number of shards
- number of replicas
- read (boolean, and only one row can be true)
Then we modify Elastic::ProxyUtil to initiate proxies from these settings.