test(e2e): bootstrap Ginkgo/Gomega framework for real APISIX scenarios

[guoqqqi]

Refs #19

Goal

Establish a Ginkgo/Gomega-based E2E foundation under test/e2e without changing the external APISIX/etcd/httpbin topology.

Scope

• add Ginkgo/Gomega dependencies
• create the suite entrypoint and shared framework helpers
• preserve current environment variables and real APISIX execution model
• provide common helpers for:
  • binary build/setup
  • admin API access
  • gateway requests
  • Eventually/Consistently style waits
  • resource cleanup
  • license-gated / capability-gated skip handling
• define a first label taxonomy such as smoke, crud, integration, slow, license-gated

Acceptance Criteria

• a minimal Ginkgo suite runs in CI against real APISIX
• at least 1-2 representative scenarios are implemented as examples
• new E2E additions have an obvious framework to follow
• current CI remains usable during migration