feat(ci): add ginkgo e2e pipeline for PRs

[sydorovdmytro]

Adds a new pipeline to run Ginkgo E2E tests

What issue type does this pull request address? (keep at least one, remove the others)
/kind enhancement

What does this pull request do? Which issues does it resolve? (use resolves #<issue_number> if possible)
resolves #

---

Note

Adds a GitHub Actions workflow and composite action to build artifacts and run labeled/dir-filtered Ginkgo E2E tests, including install/delete and upgrade checks on kind.

• CI / Workflows (.github/workflows/e2e-ginkgo.yaml):
  • Adds PR/release/dispatch-triggered E2E pipeline with concurrency control and change-detection gating.
  • Builds vcluster CLI and syncer image (Dockerfile.release, GoReleaser), uploads as artifacts.
  • Validates cluster lifecycle:
    • Install/delete tests via kubectl and helm on kind.
    • Upgrade tests from latest release → dev build across k3s and k8s distros.
  • Executes Ginkgo E2E suites via composite action with label filter parsed from PR body or input; prints diagnostics on failure.
• Composite Action (.github/actions/run-ginkgo-e2e/action.yml):
  • Supports directory- or label-based test selection; installs Ginkgo, loads artifacts, prunes Docker images.
  • Runs ginkgo with timing/progress flags and JSON report output; passes --vcluster-image to tests.
  • Generates concise failure summary from test-reports/report.json for job outputs.

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[cursor]

Bug: JSON report flag contradicts TODO comment

The comment on lines 107-108 states the --json-report flag is "temporarily disabled" due to a nil pointer issue, yet line 117 still includes --json-report=${REPORT_PATH} in the GINKGO_ARGS. This contradicts the documented intent and the TODO comment warning that this flag causes panic. Either remove the flag or remove the misleading comment.