Port the Azure Resource Explorer extension to core. (#2701)

* Port the Azure Resource Explorer extension to core.

This will enable Azure viewlet by default in the next release.

- Moving this code from the SQL Server 2019 extension to Azure Data Studio core
- Ported tests and verified they work in the integration tests.sh file
- Fixed an issue that caused integration tests to fail if you have a SQL Server 2019 big data cluster endpoint listed, but the extension isn't installed.

extensions/azurecore/tsconfig.json

@@ -0,0 +1,22 @@
+{
+	"compileOnSave": true,
+	"compilerOptions": {
+		"module": "commonjs",
+		"target": "es6",
+		"outDir": "./out",
+		"lib": [
+			"es6", "es2015.promise"
+		],
+		"typeRoots": [
+			"./node_modules/@types"
+		],
+		"sourceMap": true,
+		"emitDecoratorMetadata": true,
+		"experimentalDecorators": true,
+		"moduleResolution": "node",
+		"declaration": true
+	},
+	"exclude": [
+		"node_modules"
+	]
+}