fix: prevents memory accumulation from informers

[shawkins]

Description

I completely missed the need for cleanup with the proactive closing of informers with #5327. Unfortunately this affects both implicit and explicit usage of informers. An alternative approach is to track if the client has been closed - I had initially avoided that because it's more work, as you can see from this pr. This approach though doesn't have much risk other than some code complexity.

The only other possibility would be to track a set of informers on the BaseClient and close them using the completablefuture, but that will also require actively removing entires from the set once they've already been closed.

Fixes #5626

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]

Correction - closing the client doesn't seem to have enough of a proactive effect for the ResourceTest test to pass. The next update to the commit adds the explicit tracking of closeables to the BaseClient. For now I've left in the HttpClient close tracking as well, but it could be removed if desired.

[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

58.5% Coverage
0.0% Duplication

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