[EKS] [aws-mountpoint-s3-csi-driver]: Add podLabels support to Managed Add-on configuration schema

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**Tell us about your request**
The EKS Managed Add-on for `aws-mountpoint-s3-csi-driver` currently does not support `podLabels` in its configuration schema. The schema is defined with `additionalProperties: false`, so any fields not explicitly defined are rejected.

$ aws eks describe-addon-configuration \
--addon-name aws-mountpoint-s3-csi-driver \
--addon-version v2.3.0-eksbuild.1

Currently supported fields:

**controller:**
- `nodeSelector`
- `tolerations`

**node:**
- `nodeSelector`
- `tolerateAllTaints`
- `tolerations`
- `podInfoOnMountCompat`

There is no way to add custom labels to Pods managed by this add-on.

### Use Case:
The customer needs to add custom labels to the Mountpoint Pods (`mp-xxxxx` in `mount-s3` namespace) that are dynamically created by the CSI Driver v2 Controller. Since these Pods are dynamically created by the CSI Driver Controller (not by users directly), there is no way to pre-configure labels on them through the current Managed Add-on configuration unless to use mutating webhook.

**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?**
What outcome are you trying to achieve, ultimately, and why is it hard/impossible to do right now? What is the impact of not having this problem solved? The more details you can provide, the better we'll be able to understand and solve the problem.

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

**Additional context**
I see that `podLabels` support for Mountpoint Pods is currently being added to the Helm chart in `mountpoint-s3-csi-driver`:
- [#636](https://github.com/awslabs/mountpoint-s3-csi-driver/issues/636)
- [#714](https://github.com/awslabs/mountpoint-s3-csi-driver/pull/714)

Once this feature is available in the Helm chart, could the EKS Managed Add-on configuration schema also be updated to expose `podLabels` (specifically for `mountpointPod`) so that users deploying via the Managed Add-on can configure custom labels without needing to switch to a self-managed Helm installation?

Start by running the mentioned `aws eks describe-addon-configuration` command for the aws-mountpoint-s3-csi-driver and reviewing the linked Helm chart issue #636 and pull request #714. Done means the Managed Add-on schema exposes `podLabels` specifically for `mountpointPod`, allowing custom labels without a self-managed Helm installation.

Written by the indexing model from the issue text.