Add concurrent index resourcegroup status commitid

What does this MR do and why?

Follow up (no-op) concurrent index creation. We have already created index on production using prepare_async_index via !70279 (diffs)

How to set up and validate locally

rails db:migrate:up VERSION=20210922084115

== 20210922084115 ConcurrentIndexResourceGroupStatusCommitIdForCiBuilds: migrating
-- transaction_open?()
   -> 0.0000s
-- index_exists?(:ci_builds, [:resource_group_id, :status, :commit_id], {:where=>"resource_group_id IS NOT NULL", :name=>"index_ci_builds_on_resource_group_and_status_and_commit_id", :algorithm=>:concurrently})
   -> 0.0096s
-- execute("SET statement_timeout TO 0")
   -> 0.0005s
-- add_index(:ci_builds, [:resource_group_id, :status, :commit_id], {:where=>"resource_group_id IS NOT NULL", :name=>"index_ci_builds_on_resource_group_and_status_and_commit_id", :algorithm=>:concurrently})
   -> 0.0037s
-- execute("RESET statement_timeout")
   -> 0.0006s
== 20210922084115 ConcurrentIndexResourceGroupStatusCommitIdForCiBuilds: migrated (0.0305s)

rails db:migrate:down VERSION=20210922084115

== 20210922084115 ConcurrentIndexResourceGroupStatusCommitIdForCiBuilds: reverting
-- transaction_open?()
   -> 0.0000s
-- indexes(:ci_builds)
   -> 0.0101s
-- execute("SET statement_timeout TO 0")
   -> 0.0005s
-- remove_index(:ci_builds, {:algorithm=>:concurrently, :name=>"index_ci_builds_on_resource_group_and_status_and_commit_id"})
   -> 0.0041s
-- execute("RESET statement_timeout")
   -> 0.0005s
== 20210922084115 ConcurrentIndexResourceGroupStatusCommitIdForCiBuilds: reverted (0.0321s)

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