Fix AppX detection and add package restore support (#4842)

* Fix installed AppX package detection

* Add AppX package restore workflow

* Add AppX operation progress feedback

* Fix AppX operation launch race

* Handle AppX workflow failures

functions/private/Get-WinUtilInstalledAPPX.ps1

@@ -0,0 +1,24 @@
+function Get-WinUtilInstalledAPPX {
+    <#
+
+    .SYNOPSIS
+        Gets the names of AppX packages installed for all users
+
+    #>
+
+    # AppX module auto-loading can leave PowerShell 7 dependent on a temporary Windows PowerShell
+    # compatibility proxy. Run the query in Windows PowerShell 5.1 so it remains available after
+    # those temporary proxy files are removed.
+    $ps5Command = {
+        Get-AppxPackage -AllUsers -ErrorAction Stop | Select-Object -ExpandProperty Name
+    }
+
+    $packageOutput = powershell.exe -NoProfile -NonInteractive -Command $ps5Command 2>&1
+    if ($LASTEXITCODE -ne 0) {
+        $failureDetails = ($packageOutput | Out-String).Trim()
+        Write-WinUtilLog -Level "ERROR" -Component "AppX" -Message "Failed to get installed AppX packages: $failureDetails"
+        return @()
+    }
+
+    return @($packageOutput)
+}