arch, vmm: Move "generate_common_cpuid" from "CpuManager" to "arch"

This refactoring ensures all CPUID related operations are centralized in
`arch::x86_64` module, and exposes only two related public functions to
the vmm crate, e.g. `generate_common_cpuid` and `configure_vcpu`.

Signed-off-by: Bo Chen <chen.bo@intel.com>

arch/Cargo.toml

@@ -23,6 +23,7 @@ versionize = "0.1.6"
 versionize_derive = "0.1.4"
 vm-memory = { version = "0.5.0", features = ["backend-mmap", "backend-bitmap"] }
 vm-migration = { path = "../vm-migration" }
+vmm-sys-util = { version = ">=0.5.0", features = ["with-serde"] }
 
 [target.'cfg(target_arch = "aarch64")'.dependencies]
 fdt_parser = { version = "0.1.3", package = 'fdt'}