Improve state management implementation in the GUI

[laim2003]

Task summary

The current proposed architecture uses singletons. However, this can lead to problems in the future, e.g. for testing the state and generally, Singletons are not a good design choice for larger projects. Therefore I recommend moving to a different architecture. I recommend:

• Keep using IdeGuiStateManager, but remove singleton design and make the class and its properties fully read-only.
• Supply the IdeGuiStateManager to all components via Dependency Injection (including UI controllers.)
• Create a custom UI Controller class that takes an IdeGuiState as a parameter in the Constructor (and can be extended in individual controller implementations)
• Create a listener interface that allows components to be notified when changes to the context occur (e.g. switching a context)

Additional context

No response