[CI] Fix template to get it back to work with the megapipeline. (#20587)

* [CI] Fix template to get it back to work with the megapipeline.

The template has a parameter that allows to know the checkout location,
that allow use to reuse it in the megapiepline. The new step was added
ignoring that fact.

* Add checkout dir as requeste in the pr.

eng/pipelines/common/maui-templates.yml

@@ -104,9 +104,11 @@ jobs:
 
   - pwsh: ./build.ps1 --target=dotnet-integration-build --verbosity=diagnostic
     displayName: Build Microsoft.Maui.IntegrationTests
+    workingDirectory: ${{ parameters.checkoutDirectory }}
 
   - pwsh: ./build.ps1 --target=dotnet-integration-test --filter="FullyQualifiedName=Microsoft.Maui.IntegrationTests.TemplateTests" --resultsfilename="integration-tests" --verbosity=diagnostic
     displayName: Run $(PLATFORM_NAME) templates build tests
+    workingDirectory: ${{ parameters.checkoutDirectory }}
 
   - task: PublishTestResults@2
     displayName: Publish the $(PLATFORM_NAME) templates build tests