Add arch-agnostic traits Vm and Vcpu. Add arch-specific traits
HypervisorXXX, VmXXX, VcpuXXX, with impls for KVM.
BUG=chromium:1077058
TEST=added test for functions and structs interacting with the traits
Change-Id: I809f42f32a558c7835831c90e24fca82ce7744ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2176562
Reviewed-by: Udam Saini <udam@google.com>
Reviewed-by: Zach Reizner <zachr@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Steven Richman <srichman@google.com>
