[EKS] [EFS CSI driver add-on]: vol-metrics-opt-in flag not working

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**Tell us about your request**
The [aws-efs-csi-driver](https://github.com/kubernetes-sigs/aws-efs-csi-driver?tab=readme-ov-file#container-arguments-for-efs-plugin-of-efs-csi-node-daemonset) provides a container argument --vol-metrics-opt-in to enable metrics for EFS volumes.

As of 2.1.8-eksbuild.1, the `node.volMetricsOptIn` parameter cannot be used.

**Which service(s) is this request for?**
EKS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**

While trying to apply the following configuration:
```
{"node": {"volMetricsOptIn": true}}
```

I get the error:

```InvalidParameterException: ConfigurationValue provided in request is not supported: Json schema validation failed with error: [$.node.volMetricsOptIn: is not defined in the schema and the schema does not allow additional properties]```

**Are you currently working around this issue?**
No

**Additional context**

**Attachments**

Start with the EKS add-on configuration schema and the aws-efs-csi-driver container-arguments documentation linked in the issue. Reproduce the JSON schema validation error using node.volMetricsOptIn, then determine whether the parameter is accepted by the add-on configuration. Done means the configuration validates and enables EFS volume metrics.

Written by the indexing model from the issue text.