`import.meta.env` is supported in both vitest and webpack [as of
recent](https://github.com/webpack/webpack/pull/19996), so replace all
previous use of `process.env` with it. Current usage is limited to test
files, I've also verified it works in actual frontend code.
`webpack/module` is added to typescript types which includes the
definition for `import.meta.env`. I've also made the eslint globals more
precise. Finally, `__webpack_public_path__` is removed from our type
definitions because `webpack/module` also provides it.
None of the frontend js/ts files was touched besides these two commands
(edit: no longer true, I touched one file in
61105d0618
because of a deprecation that was not showing before the rename).
`tsc` currently reports 778 errors, so I have disabled it in CI as
planned.
Everything appears to work fine.
