KVM: x86: Initialize guest cpu_caps based on KVM support

KVM: x86: Initialize guest cpu_caps based on KVM support

Constrain all guest cpu_caps based on KVM support instead of constraining
only the few features that KVM _currently_ needs to verify are actually
supported by KVM.  The intent of cpu_caps is to track what the guest is
actually capable of using, not the raw, unfiltered CPUID values that the
guest sees.

I.e. KVM should always consult it's only support when making decisions
based on guest CPUID, and the only reason KVM has historically made the
checks opt-in was due to lack of centralized tracking.

Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-45-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>