Generate nested struct if anonymous struct or union has a field name

[lithiumtoast]

Found in SDL3:

typedef struct SDL_GamepadBinding
{
    SDL_GamepadBindingType input_type;
    union
    {
        int button;

        struct
        {
            int axis;
            int axis_min;
            int axis_max;
        } axis;

        struct
        {
            int hat;
            int hat_mask;
        } hat;

    } input;

    SDL_GamepadBindingType output_type;
    union
    {
        SDL_GamepadButton button;

        struct
        {
            SDL_GamepadAxis axis;
            int axis_min;
            int axis_max;
        } axis;

    } output;
} SDL_GamepadBinding;

    [StructLayout(LayoutKind.Explicit, Size = 32, Pack = 4)]
    public partial struct SDL_GamepadBinding
    {
        [FieldOffset(0)]
        public SDL_GamepadBindingType input_type; // size = 4

        [FieldOffset(4)]
        public SDL_GamepadBinding_Input input; // size = 12

        [FieldOffset(16)]
        public SDL_GamepadBindingType output_type; // size = 4

        [FieldOffset(20)]
        public SDL_GamepadBinding_Output output; // size = 12

        [StructLayout(LayoutKind.Explicit, Size = 12, Pack = 4)]
        public partial struct SDL_GamepadBinding_Input
        {
            [FieldOffset(0)]
            public int button; // size = 4

            [FieldOffset(0)]
            public SDL_GamepadBinding_Input_Axis axis; // size = 12

            [FieldOffset(0)]
            public SDL_GamepadBinding_Input_Hat hat; // size = 8

            [StructLayout(LayoutKind.Explicit, Size = 12, Pack = 4)]
            public partial struct SDL_GamepadBinding_Input_Axis
            {
                [FieldOffset(0)]
                public int axis; // size = 4

                [FieldOffset(4)]
                public int axis_min; // size = 4

                [FieldOffset(8)]
                public int axis_max; // size = 4
            }

            [StructLayout(LayoutKind.Explicit, Size = 8, Pack = 4)]
            public partial struct SDL_GamepadBinding_Input_Hat
            {
                [FieldOffset(0)]
                public int hat; // size = 4

                [FieldOffset(4)]
                public int hat_mask; // size = 4
            }
        }

        [StructLayout(LayoutKind.Explicit, Size = 12, Pack = 4)]
        public partial struct SDL_GamepadBinding_Output
        {
            [FieldOffset(0)]
            public SDL_GamepadButton button; // size = 4

            [FieldOffset(0)]
            public SDL_GamepadBinding_Output_Axis axis; // size = 12

            [StructLayout(LayoutKind.Explicit, Size = 12, Pack = 4)]
            public partial struct SDL_GamepadBinding_Output_Axis
            {
                [FieldOffset(0)]
                public SDL_GamepadAxis axis; // size = 4

                [FieldOffset(4)]
                public int axis_min; // size = 4

                [FieldOffset(8)]
                public int axis_max; // size = 4
            }
        }
    }