fix(vertx): VertxHttpClientFactory reuses the same Vertx instance for each VertxHttpClient instance

[manusa]

Description

Fixes #6709

Initial proposal to fix the Vertx thread-leaking issue.

• Switched Vert.x to use daemon threads
• Refactored VertxHttpClientFactory to re-use the same Vertx instance
• VertxHttpClientFactory can optionally use a user-provided and user-managed Vertx instance
• Added shutdown hook to VertxHttpClientFactory to close the default provided Vertx instance

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change
• Chore (non-breaking change which doesn't affect codebase;
  test, version modification, documentation, etc.)

Checklist

• Code contributed by me aligns with current project license: Apache 2.0
• I Added CHANGELOG entry regarding this change
• I have implemented unit tests to cover my changes
• I have added/updated the javadocs and other documentation accordingly
• No new bugs, code smells, etc. in SonarCloud report
• I tested my code in Kubernetes
• I tested my code in OpenShift

[shawkins]

LGTM, I was hoping @vietj could chime in as well as he provided the initial prototype that created an instance per factory.

[manusa]

LGTM, I was hoping @vietj could chime in as well as he provided the initial prototype that created an instance per factory.

Yup, I'd like to get his opinion too.

In any case, I think this fix shouldn't be harmful. The scenario where the factory is created multiple times (which is probably the one the fix impacts most) is leaking at the moment.
I was waiting on your approval to move forward, so unless someone else thinks this should be changed, I think we can merge (I'd really like to get out a release with the fix ASAP).

When we get Julien's comments we can adjust accordingly (it's a bad time in Europe since many have already started winter/Christmas holidays).

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
93.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud