Breaking changes of version 11.0.0

[EchoEllet]

This issue will document the breaking changes that are planned for 11.0.0

This issue will be updated as we plan. All breaking changes should be planned here instead of discussing them in different issues.

[CatHood0]

I propose that we should and need to refactor files that contain several classes that are only used internally.

If you want to see what the problem is with this you can take a look at: editor, text_line, text_block, proxy, default_styles, etc. There are many files of this style that we can perfectly divide into different files (making this avoid creating files with more than 1000 lines that are not always easy to debug)