[ui] crash with nested dropdown components

[Noaaan]

This has changed a bit. Ignoring the checkbox-specific changes, the .nested() call now requires sizing.
There is also some pitfall with the nested component, as it currently crashes when hovered 🤔
E.G.:

Components.dropdown(Sizing.content())
    .button(Text.literal("Option 1"), button -> {
        // Handle button click event
    })
    .checkbox(Text.literal("Option 2"), false, ignored -> {})
    .nested(Text.literal("Submenu"), Sizing.content(), submenu -> {
        submenu.button(Text.literal("Submenu Option"), button -> {
            // Handle submenu button click event
        });
    })
    .closeWhenNotHovered(true)
    .padding(Insets.of(5))
    .surface(Surface.TOOLTIP)

Originally posted by @Noaaan in wisp-forest/docs#12 (comment)