Upgrade react-scripts, eslint
A few upgrades while I'm in here, to react-scripts and eslint and its associates.
There are a few eslint rules I'd like to fiddle around with once this lands, but in the meantime only two warnings (react-hooks deps lists) cropped up, so I fixed them.
Test Plan: Lint, jest.
Reviewers: alangenfeld, bengotow, prha, sashank
Reviewed By: alangenfeld, prha
Differential Revision: https://dagster.phacility.com/D4438