ViewletService -> handling viewlet enabling/disabling, etc.
SidebarService -> construct sidebar composite
ActivityService -> Badge, etc

Due to issues #14151, #14149 & #14182

This reverts commit b23229f6.

This change does the following:
- filesToRestore are no longer checked at all, instead the the already existing
  editorStacks.model value from local storage restores the files just like
  normal.
- Loading of the resource is now solely the responsibility of
  TextFileEditorModel, removing a lot of the stuff being passed down through
  the layers.

Fixes #14100
Fixes #14067

fixes #7314

jsdoc was only added for the renderer side interface as they will soon
be merged together.