make VS19ExtensionVersion function

images/win/scripts/Installers/Windows2019/Validate-Wix.ps1

@@ -11,23 +11,6 @@ function Get-WixVersion {
     return $Version
 }
 
-#Gets the extension details from state.json
-function Get-WixExtensionPackage {
-    $vsProgramData = Get-Item -Path "C:\ProgramData\Microsoft\VisualStudio\Packages\_Instances"
-    $instanceFolders = Get-ChildItem -Path $vsProgramData.FullName
-
-    if($instanceFolders -is [array])
-    {
-        Write-Host "More than one instance installed"
-        exit 1
-    }
-
-    $stateContent = Get-Content -Path ($instanceFolders.FullName + '\state.packages.json')
-    $state = $stateContent | ConvertFrom-Json
-    $WixPackage = $state.packages | where { $_.id -eq "WixToolset.VisualStudioExtension.Dev16" }
-    return $WixPackage
-}
-
 $WixToolSetVersion = Get-WixVersion
 
 if($WixToolSetVersion) {
@@ -38,22 +21,14 @@ else {
     exit 1
 }
 
-$WixPackage = Get-WixExtensionPackage
-
-if($WixPackage) {
-    Write-Host "Wix Extension version" $WixPackage.version "installed"
-}
-else {
-    Write-Host "Wix Extension is not installed"
-    exit 1
-}
+$WixPackageVersion = Get-VS19ExtensionVersion -packageName "WixToolset.VisualStudioExtension.Dev16"
 
 # Adding description of the software to Markdown
 $SoftwareName = "WIX Tools"
 
 $Description = @"
 _Toolset Version:_ $WixToolSetVersion<br/>
-_WIX Toolset Visual Studio Extension Version:_ $($WixPackage.version)<br/>
+_WIX Toolset Visual Studio Extension Version:_ $WixPackageVersion<br/>
 _Environment:_
 * WIX: Installation root of WIX
 "@