Add integration tests for controller.go

[vepatel]

• Will include creating mocks and stubs for functions,
• Add tests for individual functions
  https://github.com/nginxinc/kubernetes-ingress/blob/main/internal/k8s/controller.go

To generate mocks:

• https://github.com/stretchr/testify/?tab=readme-ov-file#mock-package
• https://vektra.github.io/mockery/

### Tasks
- [ ] SPIKE - Determine complexity of add mocks for controller.go tests

[github-actions]

Hi @vepatel thanks for reporting!

Be sure to check out the docs and the Contributing Guidelines while you wait for a human to take a look at this 🙂

Cheers!