ANDROID: pkvm: x86: Enforce pVM vcpu state protection to the PV interfaces

With most of the vmexits have been handled by the pkvm hypervisor, the
pVM vcpu state can be protected against the host now. Add vcpu state
protection mechanism when loads a pkvm_vcpu. For a npVM, its vcpu is
always accessiable to the host so no protection will be performed. For
the npVM, the PV interfaces which can access the vcpu state (except
relating with the interrupt) are restricted. As the host still needs to
pre-configure pVM's vcpu state for booting, the protection is enforced
by the pkvm hypervisor only if the vcpu has started running. If the host
doesn't need to do so, then the protection can be enforced directly.

Bug: 391539939
Test: pKVM works
Upstream-Task: 402758258

Change-Id: Ibd05ebbfb376eef36e21d57ba4dd97d0b7c71d93
Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Signed-off-by: Dmytro Maluka <dmaluka@google.com>