Make workspaces code mergeable into production

[mantariksh]

Once React is rolled out, push the code that @hanstirtaputra is writing into production

[mantariksh]

Next steps for whoever picks this up

Important links

Design document
Figma

Work completed so far

@hanstirtaputra opened 7 PRs. The first 4 were approved and merged into the main branch called form-v2/form-workspaces. This code doesn't need re-review unless there are additional changes:
#4200
#4247
#4251
#4252

1 PR was opened and abandoned as we folded that functionality into another PR. This one doesn't need any followup:
#4404

Work to be done

The remaining 2 PRs have outstanding unresolved comments:
#4254
#4448

In addition, the frontend has yet to be implemented.