PDFtk actually isn't needed. It was being used for breaking a PDF
into pages but this is something that be replaced by the already present
'pdftoppm'. Furthermore, by removing this dependency we contribute to
reproducible builds and overall supply chain security because it was
obtained from gitlab with no signature verification or version pinning.
The replacement 'pdftoppm' enabled us to do a shortcut:
- before: PDF -> PDF pages -> PNG images -> RGB images
- after: PDF -> PPM images -> RGB images
And this last conversion step is trivial since the RGB format we were
using is just a PPM file without the metadata in its header.
Bump the global timeout used for various steps from 1 minute to 2
minutes. The reason is that we've seen several reports of operations
failing due to timeout reasons, that were otherwise legitimately
running.
Also, bump the timeout used for compression, which has been reported as
problematic as well.
Refs #146
Refs #149
