Support to enable asynchronous post event

[turboFei]

Why are the changes needed?

The registerAsync is not called in the code, just in UT.

This PR add an option to enable async event post for kyuubi server.

How was this patch tested?

Just add an option, the function testing has been covered by #1853.

Was this patch authored or co-authored using generative AI tooling?

No.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (2e79aa2) to head (1e5da4c).
⚠️ Report is 8 commits behind head on master.

Files with missing lines	Patch %	Lines
...in/scala/org/apache/kyuubi/config/KyuubiConf.scala	0.00%	5 Missing ⚠️
...rg/apache/kyuubi/events/EventHandlerRegister.scala	0.00%	4 Missing ⚠️
...che/kyuubi/events/ServerEventHandlerRegister.scala	0.00%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #7281   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files         697     698    +1     
  Lines       43587   43636   +49     
  Branches     5893    5894    +1     
======================================
- Misses      43587   43636   +49     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[turboFei]

thanks, merging to master and 1.11.0