KVM: selftests: Test post-KVM_RUN writes to PERF_CAPABILITIES

Now that KVM disallows changing PERF_CAPABILITIES after KVM_RUN, expand
the host side checks to verify KVM rejects any attempts to change bits
from userspace.

Link: https://lore.kernel.org/r/20230311004618.920745-18-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>