E2E next framework init

[adriankabala]

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

What does this pull request do? Which issues does it resolve? (use resolves #<issue_number> if possible) resolves # ENG-9269 ENG-9939 ENG-9940 ENG-9941

Please provide a short message that should be published in the vcluster release notes

What else do we need to know? Github workflow pipeline will be added in other PR

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[!NOTE] Introduce a new Ginkgo-based E2E test suite (vcluster/kind) with workflows, configs, and vendored deps.

• E2E Framework (Ginkgo + e2e-framework):
  • Add e2e-next/ with suite setup, vcluster/kind integration, constants (image.go, timeouts.go, cluster.go, vcluster.go), labels, and configs (kind/vcluster YAML).
  • Implement tests for core sync (test_core/sync) and deploy flows (test_deploy/*) with supporting manifests.
• CI/CD:
  • Add composite action /.github/actions/run-ginkgo-e2e and workflows /.github/workflows/e2e-ginkgo.yaml, e2e.yaml to run the E2E suite.
• Tooling/Configs:
  • Add Justfile, hack/test.sh, and golangci.yml; include e2e-next/e2e-kind.config.yaml.
• Dependencies:
  • Update go.mod/go.sum; vendor required modules (Ginkgo v2.27, Gomega v1.38, sigs.k8s.io/e2e-framework, golang.org/x/tools, etc.).

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