### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When attempting to list roles where permission boundaries are attached the response cannot be serialized 

`aws --endpoint-url=http://localhost:4566 iam list-roles --region ap-southeast-2`
```
An error occurred (InternalError) when calling the ListRoles operation (reached max retries: 2): exception while calling iam.ListRoles: Invalid type when serializing AttachedPermissionsBoundary: '<Element 'member' at 0xffff8275ef20>' cannot be parsed to structure.
```

### Expected Behavior

Expect that all roles are listed

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run localstack/localstack

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

* Create an IAM policy
* Create an IAM role which used the policy as a permission boundary
* Attempt to list all roles with `aws --endpoint-url=http://localhost:4566 iam list-roles --region ap-southeast-2`


### Environment

```markdown
- OS: MacOS
- LocalStack: latest
```


### Anything else?

_No response_
action_name: ActionNameType, resource_name: ResourceNameType, policy_statements: List[Dict]
    ) -> EvaluationResult:
        eval_res = EvaluationResult()
        eval_res["EvalActionName"] = action_name
        eval_res["EvalResourceName"] = resource_name
        eval_res["EvalDecision"] = PolicyEvaluationDecisionType.explicitDeny
        for statement in policy_statements:
            
            if (
                action_name in statement["Action"]
                and resource_name in statement["Resource"]
                and statement["Effect"] == "Allow"
            ):
                eval_res["EvalDecision"] = PolicyEvaluationDecisionType.allowed
                eval_res["MatchedStatements"] = []  
        return eval_res
    def simulate_principal_policy(
        self,
        context: RequestContext,