feat(iam): manage AWS Load Balancer Controller policy inline

[maxsxu]

Motivation

Currently, the AWS Load Balancer Controller IAM role is created, but the policy must be provided via an override or managed externally. This change manages the default AWS Load Balancer Controller policy inline within the IAM module, ensuring that the controller has the necessary permissions by default when the role is created.

Modifications

• Added aws_iam_role_policy.aws_load_balancer_controller in modules/iam/aws_load_balancer_controller.tf to define the controller policy inline.
• Updated load_balancer_policy_arn_override variable description in modules/iam/variables.tf to clarify that it's now an optional additional policy.
• Updated modules/iam/README.md to reflect the changes.

Verifying this change

• Make sure that the change passes the CI checks.

This change is already covered by existing tests, such as terraform plan in consuming modules.

Documentation

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  Managed inline in Terraform module README.