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

docs/samples/jsonrpc/netcore/executequery/jsonrpc.csproj

@@ -1,14 +1,10 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.2</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
 	  <OutputType>Exe</OutputType>
   </PropertyGroup>
   <ItemGroup>
-	<!-- <PackageReference Include="Microsoft.SqlServer.Smo" Version="12.0.2000.8" /> -->
-	<PackageReference Include="Newtonsoft.Json" Version="10.0.2" />
-	<PackageReference Include="System.Data.SqlClient" Version="4.5.1" />
-    <!-- <PackageReference Include="System.Data.SqlClient" Version="4.4.0-sqltools-24613-04" /> -->
-    <PackageReference Include="Microsoft.SqlServer.Smo" Version="140.17279.0-xplat" />
+  	<PackageReference Include="Newtonsoft.Json" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\..\..\..\src\Microsoft.SqlTools.ServiceLayer\Microsoft.SqlTools.ServiceLayer.csproj" />