Datasource/CloudWatch: Better handling of stats grouping (#24789)

* Datasource/CloudWatch: Better handling of stats grouping

package.json

@@ -208,6 +208,7 @@
     "@grafana/slate-react": "0.22.9-grafana",
     "@reduxjs/toolkit": "1.3.4",
     "@torkelo/react-select": "3.0.8",
+    "@types/antlr4": "^4.7.1",
     "@types/braintree__sanitize-url": "4.0.0",
     "@types/common-tags": "^1.8.0",
     "@types/jsurl": "^1.2.28",
@@ -221,6 +222,7 @@
     "angular-native-dragdrop": "1.2.2",
     "angular-route": "1.6.6",
     "angular-sanitize": "1.6.6",
+    "antlr4": "^4.8.0",
     "baron": "3.0.3",
     "brace": "0.11.1",
     "calculate-size": "1.1.1",