Update Infrastructure (#961)

* Update form .NET Core 2.2 to .NET Core 3.1

- Global variable for projects
- Change TFMs from netcoreapp2.2 to netcoreapp3.1
- Update global.json
- Update build.json
- Remove direct framework cake TestCore task
- Update travis dotnet version
- Update azure pipline file
- Update vscode launch.json

* Add Central Package Management

* Fix xUnit Breaking Change for MemberData type

* Fix xUnit breaking change for duplicate test method name

* Fix Rang/Index type conflict with System.Rang/Index

* Update vscode tasks.json

* Change serviceHostExecutable path in ServiceTestDriver.cs

* Downgrade SDK version (https://github.com/appveyor/ci/issues/3440)

- Appveyor hasn't installed latest SDK therefore I downgrade it until they install it.

* Dump Microsoft.SqlServer.DACFx

scripts/packages.config

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-    <package id="Cake" version="0.30.0" />
-    <package id="Newtonsoft.Json" version="9.0.1" />
-    <package id="Microsoft.Data.Tools.StringResourceTool" version="1.0.0" />
+    <package id="Cake" version="0.37.0" />
+    <package id="Newtonsoft.Json" version="12.0.3" />
+    <package id="Microsoft.Data.Tools.StringResourceTool" version="2.0.0" />
     <package id="Mono.TextTransform" version="1.0.0" />
     <package id="mssql.XliffParser" version="0.5.3" />
     <package id="mssql.ResX" version="0.2.0" />