[feat gw api] add support for infra labels + annotations

[zac-nixon]

Description

Adds support for attaching labels and annotations from the Gateway to the created TargetGroupBinding(s) for a Gateway:
https://gateway-api.sigs.k8s.io/reference/spec/#gatewayinfrastructure

I had to refactor the TargetGroupBinding manager to support changing of annotations and labels. While making these changes I backfilled tests as the TGB manager had no tests previously.

E2E tests:

• Gateway that has no labels / annotations
• Gateway that has only labels, no annotations
• Gateway that has only annotations, no labels
• Gateway that has annotations and labels
• TGB reconciles don't trigger un-neccessary patches.
• Service reconciles still work
• Ingress reconciles still work.

Tested:

apiVersion: v1
items:
- apiVersion: elbv2.k8s.aws/v1beta1
  kind: TargetGroupBinding
  metadata:
    annotations:
      annfoo3: annbar3
      elbv2.k8s.aws/checkpoint: PbfnUfSBkLuy55ms0JcKGKB5F6F8rWHDj49LCpvaRQE/5_Y2kXP4aJv81kgYF7I1U-ZE4WlqR-sLG2E-WXmJhUM
      elbv2.k8s.aws/checkpoint-timestamp: "1747837898"
    creationTimestamp: "2025-05-20T15:28:35Z"
    finalizers:
    - elbv2.k8s.aws/resources
    generation: 1
    labels:
      foo3: bar3
      gateway.k8s.aws.nlb/stack-name: test-gw-nlb
      gateway.k8s.aws.nlb/stack-namespace: gateway-nlb
    name: k8s-gatewayn-tcpapp1-0ddf17a33d
    namespace: gateway-nlb
    resourceVersion: "28321176"
    uid: 5741d762-7c62-4113-b012-44f0a1cfa91c
  spec:
    ipAddressType: ipv4
    networking:
      ingress:
      - from:
        - securityGroup:
            groupID: sg-09dbde371ea398a10
        ports:
        - port: 30265
          protocol: TCP
    serviceRef:
      name: echoserver
      port: 80
    targetGroupARN: arn:aws:elasticloadbalancing:us-east-1:565768096483:targetgroup/k8s-gatewayn-tcpapp1-8cfc832478/4a9f1df33dd36c18
    targetType: instance
    vpcID: vpc-02c95a92410c1c1f2
  status:
    observedGeneration: 1
kind: List
metadata:
  resourceVersion: ""

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: zac-nixon

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• OWNERS [zac-nixon]

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[shraddhabang]

/lgtm
/approved