add node label selectors to all CS jobs

[sdowell]

This is more flexible than the strict gke node pool selector, allowing the underlying node pools to be changed without downtime and/or coordinating changes to the prow config. Also separates presubmits from periodic nodes for better isolation/security.

[sdowell]

/assign @nan-yu /assign @karlkfi

[google-oss-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: nan-yu, sdowell

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Needs approval from an approver in each of these files: - ~~[prow/prowjobs/GoogleContainerTools/kpt-config-sync/OWNERS](https://github.com/GoogleCloudPlatform/oss-test-infra/blob/master/prow/prowjobs/GoogleContainerTools/kpt-config-sync/OWNERS)~~ [nan-yu,sdowell] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[google-oss-prow[bot]]

@sdowell: Updated the job-config configmap in namespace default at cluster default using the following files:

• key kpt-config-sync-periodics-release.yaml using file prow/prowjobs/GoogleContainerTools/kpt-config-sync/kpt-config-sync-periodics-release.yaml
• key kpt-config-sync-periodics.yaml using file prow/prowjobs/GoogleContainerTools/kpt-config-sync/kpt-config-sync-periodics.yaml
• key kpt-config-sync-postsubmits.yaml using file prow/prowjobs/GoogleContainerTools/kpt-config-sync/kpt-config-sync-postsubmits.yaml
• key kpt-config-sync-presubmits.yaml using file prow/prowjobs/GoogleContainerTools/kpt-config-sync/kpt-config-sync-presubmits.yaml
• key kpt-config-sync-terraform.yaml using file prow/prowjobs/GoogleContainerTools/kpt-config-sync/kpt-config-sync-terraform.yaml

In response to [this](https://github.com/GoogleCloudPlatform/oss-test-infra/pull/2324): >This is more flexible than the strict gke node pool selector, allowing the underlying node pools to be changed without downtime and/or coordinating changes to the prow config. Also separates presubmits from periodic nodes for better isolation/security. Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes-sigs/prow](https://github.com/kubernetes-sigs/prow/issues/new?title=Prow%20issue:) repository.