KVM: selftests: Convert pmu_event_filter_test away from VCPU_ID

Convert pmu_event_filter_test to use vm_create_with_one_vcpu() and pass
around a 'struct kvm_vcpu' object instead of using a global VCPU_ID.
Rename run_vm_to_sync() to run_vcpu_to_sync() accordingly.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>