Refactor VM config to support different CPU topologies

This is preliminary work to support crosvm's --host-cpu-topology (WIP),
which will make it possible to mirror host's CPU topology in the guest.
As a first step, we refactor AVF's system API to stop accepting number
of vCPUs as an argument, but instead only expose two topology configs:
1 vCPU (default) and matching the host's CPU topology.

For the time being, the latter results in crosvm started with `--cpu
<nproc>`.

Bug: 266664564
Test: atest -p packages/modules/Virtualization:avf-presubmit
Change-Id: I03a37be0b68b93dc0fa6e84fd51ca3bdefbe6dde
diff --git a/vmbase/example/tests/test.rs b/vmbase/example/tests/test.rs
index c6aea8c..cfb0225 100644
--- a/vmbase/example/tests/test.rs
+++ b/vmbase/example/tests/test.rs
@@ -16,7 +16,7 @@
 
 use android_system_virtualizationservice::{
     aidl::android::system::virtualizationservice::{
-        DiskImage::DiskImage, VirtualMachineConfig::VirtualMachineConfig,
+        CpuTopology::CpuTopology, DiskImage::DiskImage, VirtualMachineConfig::VirtualMachineConfig,
         VirtualMachineRawConfig::VirtualMachineRawConfig,
     },
     binder::{ParcelFileDescriptor, ProcessState},
@@ -84,7 +84,7 @@
         disks: vec![disk_image],
         protectedVm: false,
         memoryMib: 300,
-        numCpus: 1,
+        cpuTopology: CpuTopology::ONE_CPU,
         platformVersion: "~1.0".to_string(),
         taskProfiles: vec![],
     });