Fix GKE MachinePool replicas per region

[kahun]

What type of PR is this?
/kind bug

What this PR does / why we need it:
MachinePool replicas should be set based on the number of regions specified for that MachinePool.

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Fix GKE MachinePool number of replicas, now are based on the number of regions specified for that MachinePool.

[k8s-ci-robot]

Hi @kahun. Thanks for your PR.

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[cpanato]

/ok-to-test

[richardcase]

This looks good to me, after a release note update we can merge.

@kahun - could you update the release note please?

[kahun]

This looks good to me, after a release note update we can merge.

@kahun - could you update the release note please?

Done

[richardcase]

Thanks @kahun

/approve

[cpanato]

thanks
/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cpanato, kahun, richardcase

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