feat(thumbnail grid): arrow key navigation & selection history

[louisl4696]

• Added arrow key navigation for thumbnail grid Navigation with arrow keys #226
• Implemented selection history with undo/redo [Feature Request]: Selection history #1215

Summary

Arrow key navigation

Arrow keys events in MainWindow are intercepted by an eventFilter and trigger callbacks in ThumbGridLayout. Shift key events are also intercepted but do not block the event from continuing down Qt's event pipeline. Arrow key navigation mimics the behaviour of windows file explorer as outlined in #226, including multi-selection.
closes #226

Selection history

The last 30 (number chosen arbitrarily) selections are stored in a deque. Hitting R pops the most recent selection from the deque, and pushes the current selection to a second deque for redo-ing. Hitting Shift+R pops from the redo deque. It's very satisfying to use (I may be biased)
This feature could later be included into a higher level history, see #1215 for the full discussion !
Selection state changes are saved in the deques via a decorator for methods that modify the selection.
Because that includes the methods used for arrow key navigation, I wasn't able to cleanly separate these two features into two PRs... Sorry 😅

Tasks Completed

• Platforms Tested:
  • Windows x86
  • Windows ARM
  • macOS x86
  • macOS ARM
  • Linux x86
  • Linux ARM
• Tested For:
  • Basic functionality
  • PyInstaller executable