Reduce PageLayoutController and PageLayoutView dependencies
This is a follow-up to #68395 to reduce complexity and exposed public API of that change.
Even if class components have the names "controller" and "view", which implies an underlying MVC-stack, the PageLayout components are far from using the pattern. That's why it's quite fine to put processing logic to the place where it makes most sense and where dependencies and cross-calls to other objects are kept low.
This change is only about refactoring and reducing the public API in terms of information hiding and encapsulation.
Besides that the $languagesInColumnCache class variable was defined but never use - which is changed now as well.
Further flaws concerning proper record selection are part of another change.