[FEATURE] Use EKS Pod Identity for granting IAM permissions (AWS Load Balancer Controller)

[iamahgoub]

So far, the implementation has been using IRSA for granting IAM permissions needed to tools/workloads. This issue is for migrating to EKS Pod Identity (where applicable). The scope of this issue is limited to AWS LBC.

Changes:

1. Install EKS Pod Identity Agent add-on. provider-aws-eks has MR for managing EKS add-ons; see https://marketplace.upbound.io/providers/upbound/provider-aws-eks/v1.4.0/resources/eks.aws.upbound.io/Addon/v1beta1.
2. Change trust policy of the IAM role located at repos/gitops-system/tools-config/aws-load-balancer-controller-iam/.
3. Remove the ServiceAccount annotation at repos/gitops-system/tools-config/sa.yaml.
4. Add manifests for ServiceAccount and IAM role association; provider-aws-eks has MR for managing that; see https://marketplace.upbound.io/providers/upbound/provider-aws-eks/v1.4.0/resources/eks.aws.upbound.io/PodIdentityAssociation/v1beta1.