(aws-iam): (stack tags are not set for awsiam.CfnManagedPolicy)

### Describe the bug

Stack tags are not added to IAM policies, they are added to roles.

I add them to my stack like so:
```go
for tag, value := range cfg.Tags {
awscdk.Tags_Of(stack).Add(jsii.String(tag), jsii.String(value), &awscdk.TagProps{
ApplyToLaunchedInstances: jsii.Bool(true),
})
}
```

As a workaround, I tried explicitly adding them to policies like so, but, to no avail:
```go
for _, policy := range policies {
for tag, value := range cfg.Tags {
awscdk.Tags_Of(policy).Add(jsii.String(tag), jsii.String(value), &awscdk.TagProps{
ApplyToLaunchedInstances: jsii.Bool(true),
})
}
}
```

It seems like it may potentially be a gap or limit, I do not see tags available [here](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-iam-managedpolicy.html#aws-resource-iam-managedpolicy--seealso) (although Tags can be set in the AWS console for Policies).

### Expected Behavior

Stack tags are applied to managed policies

### Current Behavior

Stack tags are not applied to managed policies

### Reproduction Steps

See above sample code

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CDK CLI Version

2.147.3 (build 32f0fdb)

### Framework Version

_No response_

### Node.js Version

v20.8.0

### OS

Ubuntu 22.04.4 LTS

### Language

Go

### Language Version

1.22

### Other information

I'm using these lib versions:
```
github.com/aws/aws-cdk-go/awscdk/v2 v2.129.0
github.com/aws/aws-sdk-go v1.48.1
github.com/aws/aws-sdk-go-v2 v1.23.1
```

Start at the awsiam.CfnManagedPolicy construct and compare its stack-tag behavior with IAM roles, using the reported Go reproduction and the CloudFormation AWS::IAM::ManagedPolicy documentation. Check whether the missing tags are a CDK propagation gap or a CloudFormation limitation; done means the behavior is corrected with coverage, or the limitation is clearly documented.

Written by the indexing model from the issue text.