Add a new API version `v1alpha4` for the Backstage custom resource and update related operator scaffolding. This version will serve as the foundation for the upcoming feature e.g., enabling optional monitoring support (spec.monitoring.enabled). This ensures the immutability and clarity of previous versions.

Acceptance Criteria:

– A new directory and Go package (api/v1alpha4) exist, copied from v1alpha3.

– All version identifiers within types, registration, GroupVersionKind, and controller logic are updated from v1alpha3 to v1alpha4.

– The operator runs with both v1alpha3 and v1alpha4 versions served with correct scheme registration.

– The CRD manifest (YAML) for Backstage is updated to include v1alpha4

– NO functional or behavioral changes are introduced, v1alpha4 should perform exactly as v1alpha3 at this stage.

– All new/relevant Go unit tests pass with the new version

Notes:

– DO NOT add the monitoring/ServiceMonitor feature in this PR

– Once this issue/PR is merged, follow up with this issue https://issues.redhat.com/browse/RHIDP-5778 and its PR introducing the monitoring feature in v1alpha4 only