[EKS] [ManagedNodeGroup]: Ability to speed up the scale down phase of Managed node update process.

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**Tell us about your request**
Opened this issue on behalf of a customer.

**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?**
We have quite a few large managed node groups with 100+ nodes in each and we are trying to upgrade AMI of the managed node groups.
[UpdateConfig](https://docs.aws.amazon.com/eks/latest/APIReference/API_NodegroupUpdateConfig.html) seems to help with scale up phase, and the upgrade phase. However [Scale down phase](https://docs.aws.amazon.com/eks/latest/userguide/managed-node-update-behavior.html#managed-node-update-scale-down) seems to be slow as it does one node at a time.

`The scale down phase decrements the Auto Scaling group maximum size and desired size by one to return to values before the update started.`

Wondering if there is way or an option to speed up the scale down phase.

**Are you currently working around this issue?**
NA

**Additional context**
We are trying to upgrade AMI of the managed node groups to address Log4j vulnerability.

Start with the linked AWS UpdateConfig API reference and managed-node-update behavior documentation, focusing on how the scale-down phase is currently described for managed node groups. Determine what supported option or behavior would satisfy faster scale-down for large groups; the issue provides no repository files or tests to run.

Written by the indexing model from the issue text.