feat: add grafana alert test action [DX-5147]

[Tofel]

Create an action that allows to validate whether Grafana Alerts were firing during some time period.

Test run: https://github.com/smartcontractkit/griddle-app-test-service/actions/runs/34370101552/job/102528834799

[github-actions]

👋 Tofel, thanks for creating this pull request!

To help reviewers, please consider creating future PRs as drafts first. This allows you to self-review and make any final changes before notifying the team.

Once you're ready, you can mark it as "Ready for review" to request feedback. Thanks!

[Copilot]

🟡 Changes recommended

The README and action implementation are materially inconsistent (e.g., ctf-ref/build-from-source vs released binary), and the current runner/date behavior needs alignment to avoid broken executions.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds a new composite GitHub Action intended to act as a CD quality gate by recording Grafana alert state over a release/test window and then checking whether any watched alert was “bad” during that window.

Changes:

• Introduces ci-grafana-alert-test composite action wiring to run grafana-alertcheck in record and check modes.
• Adds documentation describing how to integrate the action into a workflow and how the gate behaves.

File summaries

File	Description
actions/ci-grafana-alert-test/README.md	Documents the new action’s purpose, usage, and operational expectations.
actions/ci-grafana-alert-test/action.yml	Implements the composite action: input validation, window resolution, binary install, record/check execution, summary output, and artifact upload on failure.

Review details

Suppressed comments (1)

actions/ci-grafana-alert-test/README.md:28

• The usage example includes ctf-ref, but action.yml does not define this input, so consumers following the example will pass an unknown input and still be running the default behavior (downloaded v0.1.0).

```yaml
- uses: smartcontractkit/.github/actions/ci-grafana-alert-test@ci-grafana-alert-test/v1
  with:
    mode: record
    grafana-url: ${{ vars.GRAFANA_URL }}
    grafana-token: ${{ secrets.GRAFANA_TOKEN }}
    alerts: |
      My Service Latency
      My Service Error Rate
    ctf-ref: <commit-sha>

• Files reviewed: 2/2 changed files
• Comments generated: 5
• Review effort level: Lite

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[Copilot]

🟡 Changes recommended

The action currently has avoidable security/robustness gaps (unsafe $GITHUB_OUTPUT write and no integrity verification of the downloaded executable) that should be addressed before relying on it as a CD quality gate.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

Suppressed comments (2)

Previously missed (2) — in code that hasn't changed since the last review.

actions/ci-grafana-alert-test/action.yml:7

• The action description hard-codes the grafana-alertcheck version (v0.1.0), but the executable version is already controlled via RELEASE_VERSION later in the file. This creates a second source of truth and will drift on version bumps (and it contradicts the README claim that the version is pinned in one place).
  actions/ci-grafana-alert-test/action.yml:367
• This action writes several outputs using >> "$GITHUB_OUTPUT". To match the preferred pattern used elsewhere in this repo and avoid subtle redirection/escaping issues, append outputs via | tee -a "$GITHUB_OUTPUT" (grouping them in a single block also keeps the step easier to maintain).

• Files reviewed: 2/2 changed files
• Comments generated: 3
• Review effort level: Lite