[Internal] for the jest portion of the tests, we should handle sigint.

[pavelfeldman]

[rwoll]

+1: I rebased some work off of main which pulled in the new runners. I ran npm run test without realizing it would run all the tests—including the headful tests. I tried to stop it with a sigint, but ultimately had to force quit the terminal.

[JoelEinbinder]

This is mostly fixed, although there a few tests which launch their own browsers that will still leak zombies if interrupted.

[aslushnikov]

Jest is gone from our tests!