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/public/Invoke-WPFAppxRemoval.ps1

@@ -96,5 +96,5 @@ function Invoke-WPFAppxRemoval {
             $sync.ProcessRunning = $false
         }
 
-    }
+    } | Out-Null
 }

functions/public/Invoke-WPFFeatureInstall.ps1

@@ -36,5 +36,5 @@ function Invoke-WPFFeatureInstall {
         Write-Host "---   Features are Installed    ---"
         Write-Host "---  A Reboot may be required   ---"
         Write-Host "==================================="
-    }
+    } | Out-Null
 }

functions/public/Invoke-WPFInstall.ps1

@@ -110,5 +110,5 @@ function Invoke-WPFInstall {
             }
             $sync.ProcessRunning = $False
         }
-    }
+    } | Out-Null
 }

functions/public/Invoke-WPFUIThread.ps1

@@ -1,3 +1,7 @@
 function Invoke-WPFUIThread ($ScriptBlock) {
+    if ($null -eq $sync.form -or $null -eq $sync.form.Dispatcher) {
+        return
+    }
+
     $sync.form.Dispatcher.Invoke([action]$ScriptBlock)
 }

functions/public/Invoke-WPFtweaksbutton.ps1

@@ -88,5 +88,5 @@ function Invoke-WPFtweaksbutton {
     Write-Host "--     Tweaks are Finished    ---"
     Write-Host "================================="
     Write-WinUtilLog -Component "Tweaks" -Message "Tweaks workflow completed."
-  }
+  } | Out-Null
 }