Add feature to update IAM policy at managed folder level

[jesayafn]

Determine this is the right repository

• I determined this is the correct repository in which to report this feature request.

Summary of the feature request

Currently, setting policy in a managed folder level requires manual REST API calls, and we need the same way to apply the policy like we applied to bucket level. Check this documentation

Desired code experience

file: main.py

   storage_control_client = storage_control_v2.StorageControlClient(credentials=credential)
        project_path = storage_control_client.common_project_path("_")    
        bucket_path = f"{project_path}/buckets/{bucket_name}"

        # Check if the path is a managed folder
        request = storage_control_v2.GetManagedFolderRequest(
            name=f"{bucket_path}/managedFolders/{path}"
        )
    managed_folder = storage_control_client.get_managed_folder(request=request)
    policy = managed_folder.get_iam_policy(requested_policy_version=3)
    policy.bindings.append({
        "role": "roles/storage.objectViewer",
        "members": ["allUsers"]
    })
    managed_folder.set_iam_policy(policy)

Expected results

The result is the same as I do on the bucket level.

API client name and version

google-cloud-storage-control 1.6.0

Use case

This feature will be useful to alter the policy at the managed folder level

Additional context

No response