KVM: x86: Route non-canonical checks in emulator through emulate_ops

Add emulate_ops.is_canonical_addr() to perform (non-)canonical checks in
the emulator, which will allow extending is_noncanonical_address() to
support different flavors of canonical checks, e.g. for descriptor table
bases vs. MSRs, without needing duplicate logic in the emulator.

No functional change is intended.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20240906221824.491834-3-mlevitsk@redhat.com


[sean: separate from additional of flags, massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>