[WIP]: --no-compat / --compat toggle flags (default: --compat)

[NullVoxPopuli]

This will be my default app, and I'd propose should become the default once we get a bit more of the ecosystem using v2 addons, we can RFC flipping the default to --no-compat

Changes:

• remove config/environment.js
• remove config/targets.js
• remove ember-cli-build.js
• remove @embroider/compat
• migrate from @embroider/compat/babel to @embroider/macros/babel
• remove @embroider/config-meta-loader
• remove ember-load-initializers
  • remove loadInitializers call in app.js/ts
• set up manual registry
  • remove compatModules from app.js/ts
  • add registry.ts to use with ember-resolver
• set up manual environment
• create test for --no-compat

old news

Requires:

• Adjust the lint command / enforce prettier in CI (our code, not for the output) #35 (else diff is too big)