4.0.0-beta.8

test(linux): cover the --reset launcher fallback (LAC-2663) (#583)

#450 was fixed by scanning process.argv when a Linux launcher strips
Chromium switches, but nothing tested it. Move the detection out of
main.js into src/main/reset-flag.js and unit test it with argv and env
faked, both with switches parsed and with them stripped the way AppImage,
Snap and Flatpak do.

Also narrows CROSSOVER_RESET: 0, false, no, off and empty now mean off.
It used to reset on any value at all, and a reset cannot be undone.