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

Directory.Build.props

@@ -1,16 +1,6 @@
 <Project>
   <PropertyGroup>
-    <MSBuildAllProjects>$(MSBuildAllProjects);$(MSBuildThisFileFullPath)</MSBuildAllProjects>
-    <SmoPackageVersion>160.2004021.0</SmoPackageVersion>
-    <SqlClientPackageVersion>1.1.1</SqlClientPackageVersion>
-    <NewtonsoftPackageVersion>11.0.1</NewtonsoftPackageVersion>
-    <DacFxPackageVersion>150.4787.1-preview</DacFxPackageVersion>
     <HighEntropyVA>true</HighEntropyVA>
     <TargetLatestRuntimePatch>true</TargetLatestRuntimePatch>
   </PropertyGroup>
-  <ItemGroup>
-    <PackageReference Include="Microsoft.Data.SqlClient" Version="$(SqlClientPackageVersion)" />
-    <PackageReference Include="Microsoft.SqlServer.SqlManagementObjects" Version="$(SmoPackageVersion)" />
-    <PackageReference Include="Microsoft.SqlServer.DacFx" Version="$(DacFxPackageVersion)" GeneratePathProperty="true" />
-  </ItemGroup>
 </Project>