CFE-1168: Add CMPSMachineNamePrefix feature-gate

[chiragkyal]

Add new CMPSMachineNamePrefix feature-gate to guard the implementation changes done to support customized control plane machine names.

• Part of CFE-1168
• Implements CFE-1166: Customizing control plane machine names enhancements#1714

[openshift-ci-robot]

@chiragkyal: This pull request references CFE-1168 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "4.18.0" version, but no target version was set.

In response to this:

Add new CMPSMachineNamePrefix feature-gate to guard the implementation changes done to support customized control plane machine names.

• Part of CFE-1168
• Implements CFE-1166: Customizing control plane machine names enhancements#1714

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[openshift-ci]

Hello @chiragkyal! Some important instructions when contributing to openshift/api:
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[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: chiragkyal
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[chiragkyal]

/assign @JoelSpeed

[openshift-ci]

@chiragkyal: The following test 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/e2e-gcp	97fe813	link	false	/test e2e-gcp

Full PR test history. Your PR dashboard.

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[chiragkyal]

/test e2e-aws-serial-techpreview