main, vmm: Add mandatory id to memory zones

In anticipation for allowing memory zones to be removed, but also in
anticipation for refactoring NUMA parameter, we introduce a mandatory
'id' option to the --memory-zone parameter.

This forces the user to provide a unique identifier for each memory zone
so that we can refer to these.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/api/openapi/cloud-hypervisor.yaml

@@ -453,9 +453,12 @@ components:
 
     MemoryZoneConfig:
       required:
+      - id
       - size
       type: object
       properties:
+        id:
+          type: string
         size:
           type: integer
           format: int64