fix: set proper desiredSize when increasing minSize

[jose-ledesma]

Description of changes:

When desiredSize is managed by external autoscaling, the ACK EKS controller will not increase minSize if it exceeds desiredSize, instead reporting the following error:

  Conditions:
    Last Transition Time:  2025-09-02T12:59:44Z
    Status:                True
    Type:                  ACK.ResourceSynced
    Message:               InvalidParameterException: Minimum capacity 2 can't be greater than desired size 1
    Status:                True
    Type:                  ACK.Terminal

This PR ensures that when minSize exceeds desiredSize, the desiredSize will be automatically adjusted to match minSize, preventing the operation from failing and ensuring successful resource updating.

[ack-prow]

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This pull-request has been approved by: jose-ledesma
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[ack-prow]

Hi @jose-ledesma. Thanks for your PR.

I'm waiting for a aws-controllers-k8s member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[knottnt]

@jose-ledesma Under what circumstances is the external autoscaler applying a desiredSize below the specified minSize for the NodeGroup? Is the external autoscaler also managing minSize and maxSize?