feat(dps-dev): Add missing registration result fields (#1313)

The service has sent these fields for a while, but we never exposed them to users for some reason. This brings our registration result class up to par with what the service sends to the SDK

Also add a small bug fix to a multiplexing client test

provisioning/provisioning-device-client/src/main/java/com/microsoft/azure/sdk/iot/provisioning/device/internal/task/ProvisioningTask.java

@@ -219,7 +219,7 @@ private void executeStateMachineForStatus(RegistrationOperationStatusParser regi
                     registrationInfo.setSubstatus(ProvisioningDeviceClientSubstatus.fromString(registrationStatus.getSubstatus()));
                     registrationInfo.setCreatedDateTimeUtc(registrationStatus.getCreatedDateTimeUtc());
                     registrationInfo.setLastUpdatesDateTimeUtc(registrationStatus.getLastUpdatesDateTimeUtc());
-                    registrationInfo.setETag(registrationStatus.getETag());
+                    registrationInfo.setETag(registrationStatus.getEtag());
 
                     if (this.securityProvider instanceof SecurityProviderTpm)
                     {