acrn-config: assign VM IDs for dynamic scenario and launch setting

When dynamically creating or adding or deleting VMs, acrn config app
will assign VM IDs for the VMs with the orders of prelaunched VMs and SOS
VM and postlaunched VMs to be consistent with the VM order of vm_configs
in vm configuration. When dynamically creating launch scripts, acrn
config app will let users to specify the VM ID before launch setting.

Tracked-On: #4641

Signed-off-by: Shuang Zheng <shuang.zheng@intel.com>
Acked-by: Terry Zou <terry.zou@intel.com>

misc/acrn-config/config_app/controller.py

@@ -84,7 +84,7 @@ class XmlConfig:
         :return: None.
         :raises: ValueError, OSError, SyntaxError.
         """
-        if self._xml_path is None:
+        if self._xml_path is None or xml is None:
             return
         try:
             self._curr_xml = xml