Move controller in core/ to a common subfolder

[MorrisJobke]

• move avatar controller to core/controller
• move setup controller to core/controller
• move user controller to core/controller
• move lost controller to core/controller
  • lostpassword.css is unneeded since Warn for password reset when files_encryption is enabled #11696 is merged - 1b50d4f
  • js is already in core/js
  • css is moved to core/css/lostpassword
  • template is moved to core/templates/lostpassword

I tested all components and also the password reset stuff. Everything works as before.

cc @PVince81 @LukasReschke @nickvergessen @rullzer @DeepDiver1975

This also makes core/ look a bit more like an app (what it actually is ;)) and clean up the structure of the folder.

[mention-bot]

By analyzing the blame information on this pull request, we identified @rullzer, @LukasReschke and @DeepDiver1975 to be potential reviewers

[rullzer]

Everything seems to still work.
Nice cleanup. 👍

[LukasReschke]

👍