chore: convert k8s-helper to singleton pattern

[tolusha]

Refactors the k8s-helper package from factory pattern (New()) to singleton pattern (GetInstance()) to ensure consistent initialization across the codebase.

Changes:

• Rename New() → GetInstance()
• Rename GetClientset() → GetClientSet() (capitalization fix)
• Rename initializeForTesting() → InitializeForTesting() (export)
• Add GetDiscoveryClient() method for discovery API access
• Add initialization checks with panic guards
• Add k8shelper.InitializeForTesting() to all test packages
• Update documentation in .claude/rules/testing.md

The singleton pattern prevents multiple k8s client instances and ensures proper test initialization order across all packages.

Assisted-by: Claude Sonnet 4.6

What does this PR do?

Screenshot/screencast of this PR

What issues does this PR fix or reference?

How to test this PR?

1. Deploy the operator:

OpenShift

oc create namespace devworkspace-controller
oc apply --server-side -f https://raw.githubusercontent.com/devfile/devworkspace-operator/refs/heads/main/deploy/deployment/openshift/combined.yaml

OPERATOR_IMAGE=<...>
sed 's|quay.io/eclipse/che-operator:next|'${OPERATOR_IMAGE}'|g' deploy/deployment/openshift/combined.yaml | oc apply --server-side -f  -
oc apply --server-side -f deploy/deployment/openshift/org_v2_checluster.yaml
oc wait checluster eclipse-che -n eclipse-che --for=jsonpath='.status.chePhase'=Active   --timeout=120s

on Minikube

./build/scripts/minikube-tests/test-operator-from-sources.sh

Common Test Scenarios

• Deploy Eclipse Che
• Start an empty workspace
• Open terminal and build/run an image
• Stop a workspace
• Check operator logs for reconciliation errors or infinite reconciliation loops

PR Checklist

As the author of this Pull Request I made sure that:

• The Eclipse Contributor Agreement is valid
• Code produced is complete
• Code builds without errors
• Tests are covering the bugfix
• The repository devfile is up to date and works
• Relevant user documentation updated
• Relevant contributing documentation updated
• CI/CD changes implemented, documented and communicated

Reviewers

Reviewers, please comment how you tested the PR when approving it.

[github-actions]

New operator image available: quay.io/eclipse/che-operator:pr-2193-arm64

[github-actions]

New operator image available: quay.io/eclipse/che-operator:pr-2193-amd64

[tolusha]

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[tolusha]

⚠️ Warning: IDE/tool configuration files detected

This PR contains changes to files in directories that are typically not intended to be committed:

• .claude/rules/testing.md

Please verify these changes are intentional.

[github-actions]

New operator image available: quay.io/eclipse/che-operator:pr-2193-arm64

[github-actions]

New operator image available: quay.io/eclipse/che-operator:pr-2193-amd64

[github-actions]

New operator image available: quay.io/eclipse/che-operator:pr-2193-arm64

[github-actions]

New operator image available: quay.io/eclipse/che-operator:pr-2193-amd64

[github-actions]

New operator image available: quay.io/eclipse/che-operator:pr-2193-arm64

[github-actions]

New operator image available: quay.io/eclipse/che-operator:pr-2193-amd64

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: rohanKanojia, tolusha

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[openshift-ci]

@tolusha: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/v19-devworkspace-happy-path	5bc3526	link	true	/test v19-devworkspace-happy-path

Full PR test history. Your PR dashboard.

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