Chore: Add test for ServiceAccount SharedIndexInformer watching resources with labelSelectors

[rohanKanojia]

Description

• Added test for SharedIndexInformer for a ServiceAccount type to monitor
  events filtered with labels across all namespaces and in a particular
  namespace to verify that the use case actually works on master.
• Minor Cleanup in DefaultSharedIndexInfomerTest to avoid code
  duplication while setting MockServer expectations

Related to #2801

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

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication