Add migration tool tests to CI pipeline

Adds a 'TestMigrationTool' job in the Test stage that runs the
migration tool Pester tests on both PowerShell Core (pwsh) and
Windows PowerShell. The job is independent of the module build
since the migration tool is a standalone script.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: adityapatwardhan

.ci/ci.yml

@@ -149,3 +149,36 @@ stages:
       displayName: AzAuth PowerShell Core on Windows
       imageName: windows-latest
       useAzAuth: true
+
+  - job: TestMigrationTool
+    displayName: Migration Tool Tests
+    pool:
+      vmImage: windows-latest
+    steps:
+    - checkout: self
+
+    - pwsh: |
+        $modulePath = Join-Path -Path $env:AGENT_TEMPDIRECTORY -ChildPath 'TempModules'
+        if (-not (Test-Path -Path $modulePath)) {
+          $null = New-Item -Path $modulePath -ItemType Directory
+        }
+        Save-Module -Name "Pester" -MaximumVersion 4.99 -Path $modulePath -Force
+      displayName: Install Pester
+
+    - pwsh: |
+        $modulePath = Join-Path -Path $env:AGENT_TEMPDIRECTORY -ChildPath 'TempModules'
+        $env:PSModulePath = $modulePath + [System.IO.Path]::PathSeparator + $env:PSModulePath
+        $results = Invoke-Pester -Path '$(Build.SourcesDirectory)/tool/migration/Tests' -PassThru
+        if ($results.FailedCount -gt 0) {
+          throw "$($results.FailedCount) migration tool test(s) failed."
+        }
+      displayName: Run migration tool Pester tests
+
+    - powershell: |
+        $modulePath = Join-Path -Path $env:AGENT_TEMPDIRECTORY -ChildPath 'TempModules'
+        $env:PSModulePath = $modulePath + [System.IO.Path]::PathSeparator + $env:PSModulePath
+        $results = Invoke-Pester -Path '$(Build.SourcesDirectory)/tool/migration/Tests' -PassThru
+        if ($results.FailedCount -gt 0) {
+          throw "$($results.FailedCount) migration tool test(s) failed."
+        }
+      displayName: Run migration tool Pester tests (Windows PowerShell)