fix: route/service still exist when deleting the Gateway

[AlinsRan]

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:

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: "2025-03-25T05:47:44Z"
gatewayAPIChannel: standard
gatewayAPIVersion: v1.2.0
implementation:
  contact: null
  organization: API7
  project: api7-ingress-controller
  url: https://github.com/api7/api7-ingress-controller.git
  version: v2.0.0
kind: ConformanceReport
mode: default
profiles:
- core:
    failedTests:
    - HTTPRouteCrossNamespace
    - HTTPRoutePathMatchOrder
    - HTTPRouteRedirectHostAndStatus
    - HTTPRouteSimpleSameNamespace
    result: failure
    skippedTests:
    - GatewayInvalidTLSConfiguration
    - GatewaySecretInvalidReferenceGrant
    - GatewaySecretMissingReferenceGrant
    - GatewaySecretReferenceGrantAllInNamespace
    - GatewaySecretReferenceGrantSpecific
    - HTTPRouteExactPathMatching
    - HTTPRouteHTTPSListener
    - HTTPRouteHeaderMatching
    - HTTPRouteHostnameIntersection
    - HTTPRouteInvalidBackendRefUnknownKind
    - HTTPRouteInvalidCrossNamespaceBackendRef
    - HTTPRouteInvalidCrossNamespaceParentRef
    - HTTPRouteInvalidNonExistentBackendRef
    - HTTPRouteInvalidParentRefNotMatchingSectionName
    - HTTPRouteInvalidReferenceGrant
    - HTTPRouteListenerHostnameMatching
    - HTTPRouteMatching
    - HTTPRouteMatchingAcrossRoutes
    - HTTPRoutePartiallyInvalidViaInvalidReferenceGrant
    - HTTPRouteReferenceGrant
    - HTTPRouteRequestHeaderModifier
    - HTTPRouteWeight
    statistics:
      Failed: 4
      Passed: 7
      Skipped: 22
  name: GATEWAY-HTTP
  summary: Core tests failed with 4 test failures.

[AlinsRan]

在一致性测试中，用例中会使用不同的 gateway 进行，以隔离环境。
由于目前只支持一个 gateway，配置的路由规则会互相影响，很大概率会失败。
后续随着 ingress 完善，集中修复即可。