this PR rebuilds our PDF experience from the ground up, solving some key problems along the way.

Using a pure rust pdf renderer means that some systemic issues caused by lb-pdf go away:

• fixes pdf from source #2417
• should fix desktop support for freebsd #2701 but I'll reach out to the OP and verify

While here I also solved some other problems:

• fixes navigate pdfs via keyboard #3386
• our previous pdf rendering did not re-render upon zoom, leading to some pixelated viewing depending on device & zoomlevel. This implementation will re-render for each zoom, including doing all the math for trackpad pinch zooms.
• this implementation also only renders the visible pages (in-case hayro performance is worse than pdfium).

Excitingly this library also paves the way for us to convert pdfs to svgs so we're just a single hacker house with @ad-tra away from having some experience where you can draw on top of PDFs. It'll likely also be possible to implement pdf search (#3365) using this crate, as I believe the crate exposes text parsing functionality (but I'll have to double check to be sure).

The hayro people caution that they haven't done any perf work yet, but a coarse comparison of rendering all the pages resulted in a faster time to first frame than pdfium (although pdfium has to sit through a dl-load syscall which is probably slow, but also for our purposes is part of the comparison).

carfax pdf hayro: 96ms
carfax pdf pdfium: 155ms