Backport Bug 1967968: Minify the pdf.js code in order to improve the loading performance

⬅️ Backport Patchset

Bookkeeping

Issue(s)

• tor-browser#xxxxx
• mullvad-browser#xyz
• https://bugzilla.mozilla.org/show_bug.cgi?id=1967968

Merge Request(s)

• tor-browser!xxxx

Upstream commits: ef623ac599345, 980b6565d011a0bfd785bff61b7f065d849ef1b2, ed7fc6f9cc112 (the latter to remove jsmin, not strictly needed)

Target Channels

• Alpha
• Stable
• Legacy

Notes

Upstream switched to Terser as a JS minifier for 148.

Rather than enabling uglify only for a release, I'd switch 147 already to Terser, as it's the upstream way to do it.

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