More menu customization options for Minecraft 24w09a.

Intro
In the most recent snapshot 24w09a the backgrounds of all menus have changed to either be gameplay when in a world or the menu panorama when in the main menu. This can make it hard to read certain menus so theres a blur option to fix this issue. While this is nice to have I think there can be a few features and options added for more user customization.

Darkness Slider
The first feature I think should be added is a darkness slider that would darken the background of all menu screens. It would be more effective for improving menu readability than blur alone and would be a nice edition for those who prefer no blur at all.

Fancy & Fast menu blur toggle.
The other feature I think should be added is an option to use a fancier blur algorithm than the one currently in the game. My understanding is that the menus currently use box blur which is cheap to render but doesn't look very good. For those who have more powerful systems and want nicer visuals a fancy and fast toggle for menu blur could fix this. Fancy menu blur would use gaussian blur while fast would use the same one we have now.