Fix UI helper errors during headless -Preset and -Config runs (#4941)

* Make UI helpers no-op when no window exists

The -Preset and -Config paths run Invoke-WinUtilAutoRun before the XAML
form is created and before PresentationCore is loaded, so every call into
Invoke-WPFUIThread failed with InvokeMethodOnNull and every call into
Set-WinUtilTweaksProgressIndicator failed to resolve [Windows.Visibility].
The errors were non-terminating, so tweaks still applied, but each run
filled the log with noise.

Loading presentationframework earlier does not help: Visibility lives in
PresentationCore, which only loads once a WPF object is instantiated, and
the XAML-named progress controls do not exist in these paths either.
Guarding the two helpers covers Invoke-WPFtweaksbutton, Invoke-WPFundoall
and Invoke-WPFFeatureInstall, which the existing per-call-site $hasUI
convention never reached.

* Suppress stray console output from automation runs

Invoke-WPFRunspace returns an IAsyncResult that no caller uses, and
Set-WinUtilRegistry was the only New-PSDrive call site that did not
suppress its output. A GUI click handler discards both, but the -Preset
and -Config paths call the workflows directly, so an async handle dump
and a PSDrive table landed in the user's log.

The handle itself is kept because pester/runspace.Tests.ps1 asserts that
Invoke-WPFRunspace returns a single IAsyncResult, so the suppression goes
at the four call sites reachable from Invoke-WinUtilAutoRun.

* Add project learning for window-free UI helpers

functions/private/Set-WinUtilRegistry.ps1

@@ -28,7 +28,7 @@ function Set-WinUtilRegistry {
     )
 
     try {
-        if(!(Test-Path 'HKU:\')) {New-PSDrive -PSProvider Registry -Name HKU -Root HKEY_USERS}
+        if(!(Test-Path 'HKU:\')) {New-PSDrive -PSProvider Registry -Name HKU -Root HKEY_USERS | Out-Null}
 
         If (!(Test-Path $Path)) {
             Write-Host "$Path was not found. Creating..."

functions/private/Set-WinUtilTweaksProgressIndicator.ps1

@@ -18,6 +18,10 @@ function Set-WinUtilTweaksProgressIndicator {
         [int]$Percent
     )
 
+    if ($null -eq $sync.form -or $null -eq $sync.form.Dispatcher) {
+        return
+    }
+
     $indicatorVisible = if ($Visible) { [Windows.Visibility]::Visible } else { [Windows.Visibility]::Collapsed }
     $indicatorLabel = $Label
     $hasLabel = $PSBoundParameters.ContainsKey('Label')