vmm: Split structs from logic that make up VmConfig

Place the data structures that are required for constructing a VmConfig
into it's own module from the logic that exists to suppot them.

This is useful as a consumer of the API can now clearly see what data
structures make up the API for creating VMs.

This has no functional change and I made no attempt to clean up the
ordering (it's as in the original file) nor any other clean up.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

vmm/src/lib.rs

@@ -74,6 +74,7 @@ pub mod seccomp_filters;
 mod serial_manager;
 mod sigwinch_listener;
 pub mod vm;
+pub mod vm_config;
 
 type GuestMemoryMmap = vm_memory::GuestMemoryMmap<AtomicBitmap>;
 type GuestRegionMmap = vm_memory::GuestRegionMmap<AtomicBitmap>;