Add enhancement for CPU-based control plane autoscaling

Extends the existing resource-based control plane autoscaling in
HyperShift to consider CPU usage in addition to memory, and allows
per-size resource fraction overrides in ClusterSizingConfiguration.

Tracking: https://issues.redhat.com/browse/OCPSTRAT-2915

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: csrwng