fix: Set parent namespace in HTTPRoutePolicy and refactor related tests

[dspo]

Type of change:

• Bugfix
• New feature provided
• Improve performance
• Backport patches
• Documentation
• Refactor
• Chore
• CI/CD or Tests

What this PR does / why we need it:

在原来的实现中，当 HTTPRoute.spec.prentRefs[] 中省略 namespace 时，HTTPRoutePolicy.status.ancestors[].ancestorRef 中的 namespace 也会被省略。而 ancestorRef 中 namespace 不应当被省略。这个 PR 修复这个问题。

另外在测试中更新了 HTTPRoute HTTPRoutePolicy 的 apply 方法和状态断言，使创建 HTTPRoute 和 HTTPRoutePolicy 更简单，断言更准确（而不是靠 ContainsSubstring 来判断状态）。

Pre-submission checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[github-actions]

conformance test report

apiVersion: gateway.networking.k8s.io/v1
date: "2025-05-30T07:47:12Z"
gatewayAPIChannel: standard
gatewayAPIVersion: v1.2.0
implementation:
  contact: null
  organization: APISIX
  project: apisix-ingress-controller
  url: https://github.com/apache/apisix-ingress-controller.git
  version: v2.0.0
kind: ConformanceReport
mode: default
profiles:
- core:
    result: partial
    skippedTests:
    - HTTPRouteHTTPSListener
    statistics:
      Failed: 0
      Passed: 32
      Skipped: 1
  name: GATEWAY-HTTP
  summary: Core tests partially succeeded with 1 test skips.