Migrate all blitz package code into the nextjs fork

[flybayer]

What do you want and why?

In order to streamline nextjs upgrades, we need to move all blitz package code into the nextjs fork. Once that is finished, we can move the nextjs fork to the top level and then merge nextjs upgrades directly into this repo.

• packages/babel-preset @flybayer [legacy-framework] move blitz babel config into nextjs fork blitz#2903
• packages/display (some or all already in next package) @beerose [legacy-framework] Move display package to nextjs fork blitz#2989
• packages/installer
• packages/generator - wait for [legacy-framework] Subtemplate management blitz#2679
• packages/cli
  • Migrate all blitz cli commands into next cli, being careful to preserve existing behavior like auto PORT detection, etc
  • packages/server (will basically become obsolete once cli package is moved)
  • inside blitz pkg cli.ts, spawn next binary and pass all args
• packages/blitz
  • Once this is removed, the nextjs/packages/next package becomes the main entry point for CLI and everything
  • Rename nextjs/packages/next to blitz in package.json name field only
  • Add babel plugin to rewrite imports from next/* to blitz/* for compatibility with people converting nextjs projects to blitz
• Migrate test/integration tests into nextjs/test/integration/
• Everything else at top level. Some things like jest config might need removed completely or merged into corresponding config in nextjs/
• Move nextjs to top level

[imcodingideas]

I was thinking about that because with this coming: https://twitter.com/leeerob/status/1458846513451384832