qml: Update focus and navigation implementation

This MR is a comprehensive patch to implement the focus reason and proper keyboard navigation.

Apologies for the redundant commit names.

TBD

• [NEXT MR] When entering a group or a playlist we lose the visual focus.
• [SOLVED] Sometimes, when navigating the top bar and switching between tabs we mysteriously lose the visual focus.
• [SOLVED] Sometimes, when switching between Grid and List on the Video / All tab we lose the visual focus.
• [SOLVED] When scrolling the grid view we mysteriously lose the visual focus.
• [ Let me know if something is not working in the comments ]