KVM: x86: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load()

KVM: x86: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load()

Fold the guts of kvm_arch_sched_in() into kvm_arch_vcpu_load(), keying
off the recently added kvm_vcpu.scheduled_out as appropriate.

Note, there is a very slight functional change, as PLE shrink updates will
now happen after blasting WBINVD, but that is quite uninteresting as the
two operations do not interact in any way.

Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20240522014013.1672962-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>