[Windows][Improvement] Split and simplify "InitializeVM.ps1" script (#3806)

* improve InitializeVM script

* Update windows2019.json

* remove configs

* resolve comments

* resolve comments; fix order

* fix templates

images/win/scripts/Installers/Install-WindowsFeatures.ps1

@@ -0,0 +1,24 @@
+# Install .NET Framework 3.5 (required by Chocolatey)
+# Explicitly install all 4.7 sub features to include ASP.Net.
+# As of  1/16/2019, WinServer 19 lists .Net 4.7 as NET-Framework-45-Features
+Install-WindowsFeature -Name NET-Framework-Features -IncludeAllSubFeature
+Install-WindowsFeature -Name NET-Framework-45-Features -IncludeAllSubFeature
+
+if (Test-IsWin16) {
+    Install-WindowsFeature -Name BITS -IncludeAllSubFeature
+    Install-WindowsFeature -Name DSC-Service
+}
+
+# Install FS-iSCSITarget-Server
+$fsResult = Install-WindowsFeature -Name FS-iSCSITarget-Server -IncludeAllSubFeature -IncludeManagementTools
+if ( $fsResult.Success ) {
+    Write-Host "FS-iSCSITarget-Server has been successfully installed"
+} else {
+    Write-Host "Failed to install FS-iSCSITarget-Server"
+    exit 1
+}
+
+Write-Host "Install Containers feature"
+Install-WindowsFeature -Name Containers
+
+Invoke-PesterTests -TestFile "WindowsFeatures" -TestName "ContainersFeature"