macosx: Refactor library window toolbar autohide in video mode, fix bugs

This PR cleans up the toolbar autohide code present in VLCLibraryWindow and moves it into its own new class, VLCLibraryWindowAutohideToolbar.

This PR also contains fixes for the toolbar not correctly re-appearing when the mouse is moving outside the VLCVOutView

With fix:

Screen_Recording_2023-01-31_at_02.06.27

Before fix:

Screen_Recording_2023-01-31_at_02.08.50

Signed-off-by: Claudio Cambra developer@claudiocambra.com