[Improvement] Use dedicated ExecutionContext for EventBus async execution

[pan3793]

Code of Conduct

• [X] I agree to follow this project's Code of Conduct

Search before asking

• [X] I have searched in the issues and found no similar issues.

What would you like to be improved?

Currently, Kyuubi EventBus uses scala.concurrent.ExecutionContext.Implicits.global to execute async event handler. Generally, it's discouraged to use that global ec, instead, we should create dedicated ec for each workload.

How should we improve?

Use dedicated ExecutionContext for EventBus async execution

Are you willing to submit PR?

• [ ] Yes. I can submit a PR independently to improve.
• [ ] Yes. I would be willing to submit a PR with guidance from the Kyuubi community to improve.
• [ ] No. I cannot submit a PR at this time.

[yikf]

What are the benefits of creating dedicated ec by self?

[pan3793]

In short, the global ec is out of control. It would be shared by the whole JVM, users or other components may use it to run heavy compute workloads, share the global ec may block others workloads or blocked by others. And, it's friendly for debugging if we separate the workloads into dedicated thread pools (ec) w/ unique thread names.