Add MigrationRunspace management to migration script functions

Start-SPMigrationGUI.ps1

@@ -800,6 +800,7 @@ $script:CurrentMappingMeta = [ordered]@{
 }
 $script:IsMigrationRunning = $false
 $script:MigrationPowerShell = $null
+$script:MigrationRunspace = $null
 $script:MigrationAsyncResult = $null
 $script:MigrationOutput = $null
 $script:MigrationTimer = $null
@@ -1107,6 +1108,10 @@ function Clear-MigrationRunState {
         $script:MigrationPowerShell.Dispose()
     }
 
+    if ($null -ne $script:MigrationRunspace) {
+        $script:MigrationRunspace.Dispose()
+    }
+
     if ($null -ne $script:MigrationOutput) {
         try {
             $script:MigrationOutput.Dispose()
@@ -1116,6 +1121,7 @@ function Clear-MigrationRunState {
     }
 
     $script:MigrationPowerShell = $null
+    $script:MigrationRunspace = $null
     $script:MigrationAsyncResult = $null
     $script:MigrationOutput = $null
     $script:MigrationCompletedHandler = $null
@@ -1207,7 +1213,13 @@ function Invoke-MigrationScript {
     }
 
     Reset-MigrationStreamPositions
+    $script:MigrationRunspace = [runspacefactory]::CreateRunspace()
+    $script:MigrationRunspace.ApartmentState = [System.Threading.ApartmentState]::STA
+    $script:MigrationRunspace.ThreadOptions = [System.Management.Automation.Runspaces.PSThreadOptions]::ReuseThread
+    $script:MigrationRunspace.Open()
+
     $script:MigrationPowerShell = [powershell]::Create()
+    $script:MigrationPowerShell.Runspace = $script:MigrationRunspace
     $script:MigrationOutput = [System.Management.Automation.PSDataCollection[psobject]]::new()
     $script:MigrationCompletedHandler = $OnCompleted
     $script:MigrationActionLabel = $ActionLabel