Refactor `Environment#stop_actions` for the CI Database split

What does this MR do?

Environment#stop_actions is going to be broken after we move the ci_* tables to a separate database, because the deployments/environments tables and the ci_builds table do NOT co-exist in the same database, meaning they can't be cross-joined with JOIN clause.

This MR refactors the batch stop operation with bulk_perform_async in Sidekiq. This approach has the following advantages:

• Since each stop action is encapsulated in a asynchronous job, the process is horizontally scalable. This is a similar approach in the pipeline schedule cron worker.
• The code is more readable and maintainable. We use Environment#stop_with_action! as the SSOT method to stop an environment, so we don't need to maintain two kinds of stop logic separately (individual vs batch).
• It's easy to extend the stop logic. We have bunch of upcoming issues for the environments automatic cleanup.

On the other hand, this approach has the following disadvantages:

• This technically embraces N+1 queries into Sidekiq jobs, therefore the total query count will increase. (However, technically N+1 can't be completely resolved because stop_action.play (Ci::PlayBuildService) is a too complicated to be preloaded/batch-execution)

Related #336435 (closed) #336427 (closed)

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Closes #336435 (closed)