add xms-ids for mixedreality (Azure#17824)

Author: LinglingTong

specification/mixedreality/resource-manager/Microsoft.MixedReality/preview/2021-03-01-preview/common.json

@@ -104,6 +104,9 @@
           "items": {
             "$ref": "#/definitions/CloudErrorBody"
           },
+          "x-ms-identifiers": [
+            "code"
+          ],
           "description": "A list of additional details about the error."
         }
       },

specification/mixedreality/resource-manager/Microsoft.MixedReality/preview/2021-03-01-preview/proxy.json

@@ -202,15 +202,21 @@
           "type": "array",
           "items": {
             "$ref": "#/definitions/LogSpecification"
-          }
+          },
+          "x-ms-identifiers": [
+            "name"
+          ]
         },
         "metricSpecifications": {
           "description": "Specifications of the Metrics for Azure Monitoring",
           "uniqueItems": false,
           "type": "array",
           "items": {
             "$ref": "#/definitions/MetricSpecification"
-          }
+          },
+          "x-ms-identifiers": [
+            "name"
+          ]
         }
       }
     },
@@ -304,7 +310,10 @@
           "type": "array",
           "items": {
             "$ref": "#/definitions/MetricDimension"
-          }
+          },
+          "x-ms-identifiers": [
+            "name"
+          ]
         },
         "lockedAggregationType": {
           "description": "Locked aggregation type of the metric",
@@ -390,6 +399,9 @@
           "items": {
             "$ref": "#/definitions/Operation"
           },
+          "x-ms-identifiers": [
+            "name"
+          ],
           "description": "List of operations supported by the Resource Provider."
         },
         "nextLink": {