Run cert-manager E2E with the Kubernetes Agent backend

[nubtron]

What does this PR do?

Runs the cert-manager Kind E2E with the Kubernetes Agent backend introduced by #24639.

• The openmetrics_endpoint (port 9402) has no matching Service, so it falls back to the pod IP of the cert-manager deployment, fetched via kubectl get pods -n cert-manager --selector app.kubernetes.io/component=controller (falling back to --selector app=cert-manager if no pods match). The Agent now scrapes http://{controller_ip}:9402/metrics from inside the cluster instead of through a kubectl port-forward tunnel.
• Removes the ExitStack/port_forward setup; the Agent runs in a pod inside the kind cluster (agent_type: kubernetes), eliminating the port-forward startup race.

Motivation

Reduces Kind E2E flakes caused by the Agent running outside the cluster with port forwarding, which introduces startup races (e.g. Connection refused to the forwarded endpoint). Running the Agent inside the cluster removes the port-forward dependency. See the cert-manager master flake on 2026-08-12 (test_check_ok — Connection refused to http://10.1.0.253:36415/metrics), which is exactly the class this conversion eliminates.

Follows the same pattern already applied to argo_workflows (#24827), fluxcd (#24829), and weaviate (#24830), plus the pod-IP fallback pattern from velero (#24645) for the port with no Service.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add qa/required if this PR needs QA validation, or qa/skip-qa if it does not. Exactly one of the two is required.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[datadog-prod-us1-4]

⚠️ Warnings

🚦 4 Pipeline jobs failed

PR | test / test (linux, ubuntu-22.04, cert_manager, cert-manager (py3.13), py3.13) / cert-manager (py3.13)-py3.13 — 🔧 Needs a code fix, caused by this PR

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Linting failed due to import block being un-sorted or un-formatted in tests/conftest.py:4:1.

PR | test / test-minimum-base-package (linux, ubuntu-22.04, cert_manager, cert-manager (py3.13), py3.13) / minimum-base-package-cert-manager (py3.13)-py3.13 — 🔧 Needs a code fix, caused by this PR

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Linting failed due to unsorted import block in tests/conftest.py:4:1. Please run 'ddev test --fmt cert_manager' to fix formatting issues.

PR | test / check

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Job did not run: blocked by a failed job in an earlier pipeline stage.

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CI on my pull request is failing. Help me find and fix the root cause of each failing job below — they were flagged as caused by changes in this PR, so focus on the diff. For each job, explain the failure and propose a fix.

Branch: nubtron/cert-manager-kubernetes-agent-e2e

PR | test / test (linux, ubuntu-22.04, cert_manager, cert-manager (py3.13), py3.13) / cert-manager (py3.13)-py3.13
Commit: da26c1e21729ef6a030ff7b95c3097741d5eaafa
Error (code / quality):
Linting failed due to import block being un-sorted or un-formatted in tests/conftest.py:4:1.
CI job: https://github.com/DataDog/integrations-core/actions/runs/32128640155/job/95684789024

PR | test / test-minimum-base-package (linux, ubuntu-22.04, cert_manager, cert-manager (py3.13), py3.13) / minimum-base-package-cert-manager (py3.13)-py3.13
Commit: da26c1e21729ef6a030ff7b95c3097741d5eaafa
Error (code / quality):
Linting failed due to unsorted import block in tests/conftest.py:4:1. Please run 'ddev test --fmt cert_manager' to fix formatting issues.
CI job: https://github.com/DataDog/integrations-core/actions/runs/32128640155/job/95684789103

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[dd-octo-sts]

Validation Report

Validation	Description	Status
qa-label	Validate the pull request declares whether it needs QA for the next Agent release	❌

Run ddev validate all changed --fix to attempt to auto-fix supported validations.

Passed validations (20)

Validation	Description	Status
agent-reqs	Verify check versions match the Agent requirements file	✅
ci	Validate CI configuration and code coverage settings	✅
codeowners	Validate every integration has a CODEOWNERS entry	✅
config	Validate default configuration files against spec.yaml	✅
dep	Verify dependency pins are consistent and Agent-compatible	✅
http	Validate integrations use the HTTP wrapper correctly	✅
imports	Validate check imports do not use deprecated modules	✅
integration-style	Validate check code style conventions	✅
jmx-metrics	Validate JMX metrics definition files and config	✅
labeler	Validate PR labeler config matches integration directories	✅
legacy-signature	Validate no integration uses the legacy Agent check signature	✅
license-headers	Validate Python files have proper license headers	✅
licenses	Validate third-party license attribution list	✅
metadata	Validate metadata.csv metric definitions	✅
models	Validate configuration data models match spec.yaml	✅
openmetrics	Validate OpenMetrics integrations disable the metric limit	✅
package	Validate Python package metadata and naming	✅
readmes	Validate README files have required sections	✅
saved-views	Validate saved view JSON file structure and fields	✅
version	Validate version consistency between package and changelog	✅

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