Add BITS transfer priority configuration support

Introduces a new parameter to control BITS download priority across the build system and UI, allowing users to optimize transfer speeds when needed.

The feature adds a priority selector to the UI with four options (Foreground, High, Normal, Low) and propagates the selection through the build script and common modules. Priority can be set via UI, command-line parameter, or environment variable, with Normal as the default.

Updates the BITS transfer retry logic to respect the configured priority instead of hardcoding Normal priority, and fixes minor code formatting inconsistencies.

FFUDevelopment/FFU.Common/FFU.Common.Core.psm1

@@ -12,6 +12,10 @@ $script:CommonCoreLogFilePath = $null
 # Mutex for log file access
 $script:commonCoreLogMutexName = "Global\FFUCommonCoreLogMutex" # Unique name
 $script:commonCoreLogMutex = New-Object System.Threading.Mutex($false, $script:commonCoreLogMutexName)
+$script:BitsTransferPriority = 'Normal'
+if (-not [string]::IsNullOrWhiteSpace($env:FFU_BITS_PRIORITY)) {
+    $script:BitsTransferPriority = $env:FFU_BITS_PRIORITY
+}
 
 # Function to set the log file path for this module
 function Set-CommonCoreLogPath {
@@ -30,7 +34,24 @@ function Set-CommonCoreLogPath {
         Write-Warning "Set-CommonCoreLogPath called with an empty or null path."
     }
 }
-
+        
+function Set-BitsTransferPriority {
+    [CmdletBinding()]
+    param(
+        [Parameter(Mandatory = $true)]
+        [ValidateSet('Foreground', 'High', 'Normal', 'Low')]
+        [string]$Priority
+    )
+    $script:BitsTransferPriority = $Priority
+    try {
+        Set-Item -Path Env:FFU_BITS_PRIORITY -Value $Priority -ErrorAction Stop
+    }
+    catch {
+        WriteLog "Failed to set FFU_BITS_PRIORITY environment variable: $($_.Exception.Message)"
+    }
+    WriteLog "BITS transfer priority set to $Priority."
+}
+        
 # Centralized WriteLog function
 function WriteLog {
     [CmdletBinding()]
@@ -143,9 +164,23 @@ function Start-BitsTransferWithRetry {
         [string]$Source,
         [Parameter(Mandatory = $true)]
         [string]$Destination,
-        [int]$Retries = 3
+        [int]$Retries = 3,
+        [ValidateSet('Foreground','High','Normal','Low')]
+        [string]$Priority
     )
 
+    if ([string]::IsNullOrWhiteSpace($Priority)) {
+        if (-not [string]::IsNullOrWhiteSpace($env:FFU_BITS_PRIORITY)) {
+            $Priority = $env:FFU_BITS_PRIORITY
+        }
+        elseif (-not [string]::IsNullOrWhiteSpace($script:BitsTransferPriority)) {
+            $Priority = $script:BitsTransferPriority
+        }
+        else {
+            $Priority = 'Normal'
+        }
+    }
+
     $attempt = 0
     $lastError = $null
     $notLoggedOnHResult = [int]0x800704dd
@@ -158,7 +193,7 @@ function Start-BitsTransferWithRetry {
             $VerbosePreference = 'SilentlyContinue'
             $ProgressPreference = 'SilentlyContinue'
 
-            Start-BitsTransfer -Source $Source -Destination $Destination -Priority Normal -ErrorAction Stop
+            Start-BitsTransfer -Source $Source -Destination $Destination -Priority $Priority -ErrorAction Stop
             
             $ProgressPreference = $OriginalProgressPreference
             $VerbosePreference = $OriginalVerbosePreference
@@ -259,7 +294,7 @@ function ConvertTo-SafeName {
     # Collapse multiple consecutive dashes
     $sanitized = $sanitized -replace '-{2,}', '-'
     # Trim leading/trailing spaces, periods, and dashes
-    $sanitized = $sanitized.Trim(' ','.','-')
+    $sanitized = $sanitized.Trim(' ', '.', '-')
     if ([string]::IsNullOrWhiteSpace($sanitized)) {
         $sanitized = 'Unnamed'
     }