[release-4.18]: add OnClusterBuilds to default config

[cheesesashimi]

This effectively makes OnClusterBuild no longer require TechPreviewNoUpgrade to be enabled before making use of this feature in 4.18.z. Similar work has already landed in 4.19.

[openshift-ci]

Hello @cheesesashimi! Some important instructions when contributing to openshift/api:
API design plays an important part in the user experience of OpenShift and as such API PRs are subject to a high level of scrutiny to ensure they follow our best practices. If you haven't already done so, please review the OpenShift API Conventions and ensure that your proposed changes are compliant. Following these conventions will help expedite the api review process for your PR.

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[sergiordlr]

Verified using IPI on AWS

All MCO e2e OCB test cases pased

[cheesesashimi]

/test e2e-gcp

[openshift-ci]

@cheesesashimi: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/okd-scos-e2e-aws-ovn	34bde19	link	false	/test okd-scos-e2e-aws-ovn
ci/prow/e2e-gcp	34bde19	link	false	/test e2e-gcp

Full PR test history. Your PR dashboard.

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. I understand the commands that are listed here.

[craychee]

I am @craychee and I approve this change.

[nstielau]

+1

[JoelSpeed]

/override ci/prow/verify-crd-schema
/override ci/prow/verify

/lgtm

[openshift-ci]

@JoelSpeed: Overrode contexts on behalf of JoelSpeed: ci/prow/verify, ci/prow/verify-crd-schema

In response to this:

/override ci/prow/verify-crd-schema
/override ci/prow/verify

/lgtm

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.

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cheesesashimi, JoelSpeed

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [JoelSpeed]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[openshift-bot]

[ART PR BUILD NOTIFIER]

Distgit: ose-cluster-config-api
This PR has been included in build ose-cluster-config-api-container-v4.18.0-202507112033.p0.gc86d806.assembly.stream.el9.
All builds following this will include this PR.