Go full in on the app directory (change all generator and builder to app directory only)

[tordans]

While reviewing at #4146 which introduces a starter template for the app directory, I wonder if it is manageable for Blitz to support both the pages and the app directory/router. I feel like supporting both "worlds" adds too much maintenance burden to Blitz.

My take is, to go full in on the app directory. That will be what NextJS will focus on, and it is the better developer experience (once it is up and running).

For existing pages-apps, that change would mean that using the latest blitz betas will basically break the generators. However, I assume that existing apps will have established components and be able to compensate the lack of generators.

Part of this change would be

• change the starter templates to app directory only
• change the generators to app directory only
• embrace server components where feasible (layout and pages mainly)
• update the docs to app directory only

What do you think?