feat(editor): Implement new app layout

[MiloradFilipovic]

Summary

Implementing new app layout that will enable AI Assistant sidebar to render alongside the rest of the app. This also moves all modals to the app grid but leaves the option to still teleport them to the body if we want them to overlay everything else. See Linear ticket for details.

Related Linear tickets, Github issues, and Community forum posts

Closes ADO2-62

Review / Merge checklist

• [ ] PR title and summary are descriptive. (conventions)
• [ ] Docs updated or follow-up ticket created.
• [ ] Tests included.
• [ ] PR Labeled with release/backport (if the PR is an urgent fix that needs to be backported)