Most of the initial pdfio was moved to vcl as vcl::filter::PDFDocument.
A small part was left here, because it depended on NSS. Then later the
NSS bits were moved to svl::crypto::Signing. The rest is just a small
amount of code, keeping that separate from PDFSignatureHelper, which is
its only user makes little sense.
With this, vcl::filter::PDFDocument is an implementation detail of
PDFSignatureHelper during signature verification.
Change-Id: I6230f9e46deeff7159970f88dbb3bd2de0e9ce7d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/103350
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>