Azure: add PostgresSQL support and refactor to use resource graph (#8046)

* Azure: add PostgresSQL support and refactor to use resource graph
- Refactored to use @azure/arm-resourcegraph for all queries
- Refactored database lookup to do just 2 queries
(all servers, all DBS) instead of waiting serially on 1 query per RG
- Added Azure Database for PostgresSQL Servers support in the tree
- Removed use of older azure APIs in preference to ones compatible with resource graph
- Note: Had to use v1.0 of new subscriptions package because resourcegraph is 2month out of date vs all other packages

extensions/azurecore/package.json

@@ -173,10 +173,9 @@
     "hasAzureResourceProviders": true
   },
   "dependencies": {
+    "@azure/arm-resourcegraph": "^2.0.0",
+    "@azure/arm-subscriptions": "1.0.0",
     "adal-node": "^0.1.28",
-    "azure-arm-resource": "^7.0.0",
-    "azure-arm-sql": "^5.0.1",
-    "ms-rest": "^2.5.0",
     "request": "2.88.0",
     "vscode-nls": "^4.0.0"
   },
@@ -184,9 +183,9 @@
     "@types/mocha": "^5.2.5",
     "@types/node": "^10.12.12",
     "@types/request": "^2.48.1",
+    "mocha": "^5.2.0",
     "mocha-junit-reporter": "^1.17.0",
     "mocha-multi-reporters": "^1.1.7",
-    "mocha": "^5.2.0",
     "should": "^13.2.1",
     "typemoq": "^2.1.0",
     "vscode": "1.1.26"