Migrate validation to Pester (#1249)

* remove Validate-* scripts

* Remove references to validation scripts from .json files

* Separate "It"s by new lines

* Remove new line before the first  "It"

* Separate "It"s by new lines

* remove 32-bit WinAppDriver check

* remove explicit variable definition

Co-authored-by: Sergey Dolin <v-sedoli@micorosoft.com>

images/win/scripts/Tests/Wix.Tests.ps1

@@ -0,0 +1,23 @@
+Describe "Wix" {
+    BeforeAll {
+      $regKey = "HKLM:\Software\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall\*"
+      $installedApplications = Get-ItemProperty -Path $regKey
+      $version = ($installedApplications | Where-Object { $_.DisplayName -and $_.DisplayName.toLower().Contains("wix") } | Select-Object -First 1).DisplayVersion
+    }
+
+    It "Wix Toolset version from registry" {
+      $version | Should -Not -BeNullOrEmpty
+    }
+
+    It "Wix Toolset version from system" {
+      if (Test-IsWin19)
+      {
+        $exVersion = Get-VSExtensionVersion -packageName "WixToolset.VisualStudioExtension.Dev16"
+      }
+      else
+      {
+        $exVersion = Get-VSExtensionVersion -packageName "WixToolset.VisualStudioExtension.Dev15"
+      }
+      $exVersion | Should -Not -BeNullOrEmpty
+    }
+}