🐛fix: Clamp nodegroup desiredSize and skip when externally managed

[Minh-Ng]

What type of PR is this?
/kind bugx

What this PR does / why we need it:

When cluster autoscaler manages node scaling for AWSManagedMachinePool, we should not call UpdateNodeGroupConfig with desired replica counts. Similarly if we update a min/max size, it should change the desired size appropriately. Same goes for AWSMachinePool

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #5746

Special notes for your reviewer:

Checklist:

• squashed commits
• includes documentation
• includes emoji in title
• adds unit tests
• adds or updates e2e tests

Release note:

[k8s-ci-robot]

Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

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[k8s-ci-robot]

@Minh-Ng: The label(s) kind/bugx cannot be applied, because the repository doesn't have them.

Details

In response to this:

What type of PR is this?
/kind bugx

What this PR does / why we need it:

When cluster autoscaler manages node scaling, we should not call UpdateNodeGroupConfig with desired replica counts. Similarly if we update a min/max size, it should change the desired size appropriately.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

Checklist:

• squashed commits
• includes documentation
• includes emoji in title
• adds unit tests
• adds or updates e2e tests

Release note:

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @Minh-Ng. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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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Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.