fix #4985: triggering the cleanup of the idle task

[shawkins]

Description

Fix #4985

A thread is held per connectionpool to clean idle connections on quarkusio/quarkus#18973 we noticed that this is holding a quarkus classloader that eventually run tests out of memory. There seems to be only two ways to address this immediately:

1. trigger the cleanup when the pool is empty with a notification that will wake up the job and let it exit. This is of course not a full fledged part of their api and does change between versions, such that we have to get a hold of a different object. This is the initial proposal.
2. Add logic that will provide more control over the idle timeout on the ConnectionPool - those are arguments to the pool constructor that can then be provided to the okhttp client builder. However I'm not sure there's a good value we can always set, it seems like it would be dependent upon whether you were running in such a way as to expect lots of client creation.

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

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

62.5% Coverage
0.0% Duplication