WIP: feat!: React 19 support

[AlessioGr]

To fix

• Bunch of todos for our react-select and react-datepicker packages which are having type issues. Other dependencies seem fine
• createPortal usages throw type errors, as 2 duplicate versions of @types/react are installed which are conflicting. Looks like the pnpm override does not override the version of all peerdeps. Will likely be resolved once the official types have been published and we do not need this cursed pnpm override.
• That cursed pnpm override breaks next dev. You can get next dev to work by removing it in the workspace root package.json and installing the stable versions of @types/react and @types/react-dom. This then breaks build, though. Opened an issue with reproduction in the next repo: https://github.com/vercel/next.js/issues/65957