tests(fix): conformance tests pass

[programmer04]

What this PR does / why we need it:

Followup for

• fix(conformance): fix panic for make test.conformance #265

This PR contains several fixes that make make tests.conformance pass and generate a report.

Please check on your machine too we don't run them in CI currently.

Fixes

• adds metallb to a testing stack (without its gateway stuck, because it can't create a Service of type LoadBalanceer successfully)
• adjustment for configuring and starting a test suite that uses the newest, streamlined API of GWAPI
• some tests have to be disabled
  • conformance: HTTPRouteHTTPSListener test #269
  • conformance: HTTPRouteHostnameIntersection test  #270
  • conformance: HTTPRouteInvalidBackendRefUnknownKind tests #271
  • conformance: HTTPRouteListenerHostnameMatching test #273
  • conformance: HTTPRouteObservedGenerationBump test #274

Generated report

apiVersion: gateway.networking.k8s.io/v1alpha1
date: "2024-05-20T14:18:35+02:00"
gatewayAPIChannel: experimental
gatewayAPIVersion: v1.1.0
implementation:
  contact:
  - github.com/kong/gateway-operator/issues/new/choose
  organization: Kong
  project: gateway-operator
  url: github.com/kong/gateway-operator
  version: v1.2.2-39-g8f28499
kind: ConformanceReport
mode: default
profiles:
- core:
    result: partial
    skippedTests:
    - GatewayInvalidTLSConfiguration
    - GatewayModifyListeners
    - GatewayWithAttachedRoutes
    - HTTPRouteHTTPSListener
    - HTTPRouteHeaderMatching
    - HTTPRouteHostnameIntersection
    - HTTPRouteInvalidBackendRefUnknownKind
    - HTTPRouteListenerHostnameMatching
    - HTTPRouteObservedGenerationBump
    statistics:
      Failed: 0
      Passed: 24
      Skipped: 9
  name: GATEWAY-HTTP
  summary: Core tests partially succeeded with 9 test skips.

Which issue this PR fixes

Closes #264

[czeslavo]

Nice 🎖️