Resolve "Update packages"

Updates: helmet, typescript, jest, ts-jest, @types/jest, @typescript-eslint/eslint-plugin, @typescript-eslint/parser, eslint, json-parse-even-better-errors, node-schedule, json2csv (deprecated)

All major server packages except passport-related packages and typeorm. Some test/lint-related packages could still be upgraded. I think we can consider closing #370 (closed) unless we want to consider upgrading passport/typeorm as part of that issue as well. I foresee more effort being required to upgrade typeorm/passport since they're more intertwined with our systems.

Closes #370 (closed)