*Follow-up to PR 8909.*
This requires us to pass around `pdfFunctionFactory` to quite a lot of existing code, however I don't see another way of handling this while still guaranteeing that we can access `PDFFunction` as freely as in the old code.
Please note that the patch passes all tests locally (unit, font, reference), and I *very* much hope that we have sufficient test-coverage for the code in question to catch any typos/mistakes in the re-factoring.