Issue #3048947 by Pancho, wizonesolutions: Refactor HandlePdfController::populatePdf()

fillpdf.services.yml

src/Controller/HandlePdfController.php

src/FieldMapping.php

src/FieldMapping/ImageFieldMapping.php

src/FieldMapping/TextFieldMapping.php

src/FillPdfBackendManager.php

src/FillPdfBackendPluginInterface.php

src/FillPdfContextManagerInterface.php

src/OutputHandler.php

src/Plugin/FillPdfBackend/FillPdfServiceFillPdfBackend.php

src/Plugin/FillPdfBackend/LocalFillPdfBackend.php

src/Plugin/FillPdfBackend/LocalService.php

src/Plugin/FillPdfBackend/PdftkFillPdfBackend.php

src/TokenResolver.php

src/TokenResolverInterface.php