Test Connection operation for PowerShell connectors

Most UNIFYBroker agents have a Test Connection operation, but this can't be configured for PowerShell connectors.  This morning my customer's PowerShell connectors were failing because Azure was reporting the MS Graph API to be overloaded and only accepting admin connections (“53300: remaining connection slots are reserved for non-replication superuser connections”).

Add a Test Connection facility to a PowerShell connector.  This would tie in with https://voice.unifysolutions.net/en/communities/6/topics/4220-scheduled-execution-of-test-connection-on-agents