KVM: SEV: Add quad-underscore version of VM-scoped APIs to detect SEV+ guests

KVM: SEV: Add quad-underscore version of VM-scoped APIs to detect SEV+ guests

Add "unsafe" quad-underscore versions of the SEV+ guest detectors in
anticipation of hardening the APIs via lockdep assertions.  This will allow
adding exceptions for usage that is known to be safe in advance of the
lockdep assertions.

Use a pile of underscores to try and communicate that use of the "unsafe"
shouldn't be done lightly.

No functional change intended.

Link: https://patch.msgid.link/20260310234829.2608037-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>