promote kep-3673 to GA

[pacoxu]

• One-line PR description: kep 3673 GA

• Issue link: Kubelet limit of Parallel Image Pulls #3673

• Other comments: for GA, we change default behavior to serializeImagePulls: false and maxParallelImagePulls: 2.

[pacoxu]

/cc @ruiwen-zhao
/assign @wojtek-t @SergeyKanzhelev

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[SergeyKanzhelev]

/lgtm
/approve

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: mrunalp, pacoxu, SergeyKanzhelev
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[wojtek-t]

Hmm - do we really want to change the default for "GA"?

With https://github.com/kubernetes/enhancements/tree/master/keps/sig-architecture/5241-beta-featuregate-promotion-requirements, we generally want the GA to effectively be kind of "no-op". Changing the default might be a bit unexpected here.

I know that it doesn't explicitly affect the user (it may affect them implicitly because some pods startup (due to image pulling) may be slower/faster), but still it might not be intuitive.

Let me ping other PRR approvers about it for their thoughts.

[pacoxu]

If so, should we make this step as beta-2 for this KEP to change the default?