features: add installer replacement feature gates

[patrickdillon]

Installer feature gates need to have "install" in the title for the test analyzer. This commit adds feature gates for AWSClusterHostedDNSInstall, GCPClusterHostedDNSInstall, and GCPCustomAPIEndpointsInstall to replace their counterparts without the -install suffix, which will be removed in a follow up PR.

[openshift-ci]

Hello @patrickdillon! 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.

[sadasu]

#2300 depends on this and has to be rebased to use the new feature gate name after this PR merges.

[JoelSpeed]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[openshift-ci-robot]

/retest-required

Remaining retests: 0 against base HEAD 92b1455 and 2 for PR HEAD 4f089ea in total

[openshift-ci]

@patrickdillon: all tests passed!

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[openshift-bot]

[ART PR BUILD NOTIFIER]

Distgit: ose-cluster-config-api
This PR has been included in build ose-cluster-config-api-container-v4.20.0-202507290444.p0.g6d3c4e2.assembly.stream.el9.
All builds following this will include this PR.