Restart plugins on error

[mariusandra]

Changes

• Restart posthig-plugin-server in case it crashes. For example: the process runs out of memory on a tiny node. This way event ingestion might resume automatically. Running the bin/posthog-plugin-server script and pressing CTRL+C still stops the script like before. Just now if the node script gets killed, it'll restart. I tried this via pm2, but couldn't its "no-daemon" mode is actually just "print logs" and was too tricky to work around.
• Also updated posthog-plugin-server to 0.4.3, which supports getting all the config from $CONFIG directly. This still seems like the safest way to export settings from django other than making a custom script. This print_settings has some formats other than JSON, but none I would feel comfortable piping to bash to export as envs. Too many serialisation and string escaping issues this can run into that I'd just avoid.

WIP since I want to still test this in the heroku review app manually.

Checklist

• All querysets/queries filter by Organization, by Team, and by User
• Django backend tests
• Jest frontend tests
• Cypress end-to-end tests

[mariusandra]

The heroku review app seems to work well. This can be reviewed!