Support for using instance template as an input for machine profile in Google Cloud

With this feature, you can now use an instance template as machine profile input, in addition to VM and OS disk. 

Any ProvScheme or CustomProperty value in machine profile input are treated as default, unless overwritten by ProvScheme level or CustomProperty explicitly. After the creation of a machine catalog, you can use instance template as a machine profile input to overwrite the existing machine profile value and ProvScheme configuration.