[TRI-703] Chore: update webapp to Remix 2.0.1

[ericallam]

We're already using most of Remix's v2 features, as future flags in our remix.config.js.

How to

1. Read Remix's recommendations in the v2 release
2. They recommend upgrading to 1.19.3 first: npx upgrade-remix 1.19.3.
3. Upgrading to v2_meta and v2_headers. These should be trivial as I don't think we use the headers function anywhere, and every route on the site requires login so only the root.tsx meta function is being used right now.
4. Upgrade Remix to v2.0.1.
5. Run pnpm run typecheck --filter webapp to find and fix TypeScript errors.
6. Run the webapp and check it functions as expected

Please follow the contribution guide development section to setup and run the web app.

_{From SyncLinear.com | TRI-703}

[Rutam21]

I would love to work on this. Please assign this to me. Thanks!

CC: @ericallam @matt-aitken

[nicktrn]

Completed in c0f9f10