Windows Secure Cotnainer Executor: Add checks to validate that the wsce-site.xml is write restricted to Administrators only

The wsce-site.xml containes the impersonate.allowed and impersonate.denied keys that restrict/control the users that can be impersonated by the WSCE containers. The impersonation frameworks in winutils should validate that only Administrators have write control on this file.

This is similar to how LCE is validating that only root has write permissions on container-executor.cfg file on secure Linux clusters.