Feat: implement custom property ordering system

[dimbodek]

Description

This PR introduces a robust, zero-allocation property ordering system for the Inspector. It allows developers to explicitly define the rendering order of serialized fields without relying on their declaration order in the script.

Changes Made

• Added [Sortable] attribute: A class-level opt-in attribute. Properties will only be sorted if the parent class is marked with this attribute, ensuring zero performance overhead for standard classes.

• Added [Order(int)] attribute: A field-level attribute to define explicit rendering priority. Lower numbers are drawn first.

• Modified ToolboxPropertyHandler.cs:

  • Caches the [Order] attribute data.

  • Provides a static, zero-GC Comparison delegate (ToolboxPropertyHandler.Comparison) to prevent memory allocations during Inspector repaints.

• Updated ToolboxEditorGui.cs:

  • Modified DrawPropertyChildren to support dynamic sorting.

  • Implemented ListPool to collect properties without generating garbage.

  • Default properties (without [Order]) retain their natural index but are shifted (propsList.Count + 1) to ensure [Order(0)] always takes absolute priority and is pushed to the very top.

Usage Example

To enable sorting, the class must be marked with [Sortable]. Fields can then be reordered using [Order(int)], regardless of where they are declared in the code.

using UnityEngine;

[Sortable] // 1. Opt-in for sorting on the class level
public class CustomOrderingExample : MonoBehaviour
{
    // Declared FIRST in the script, but will be drawn later in the Inspector
    // because they don't have an explicit Order attribute.
    public int someStandardValue = 10;
    public float anotherStandardValue = 20.5f;

    // Declared in the middle, but will be pushed to the very bottom
    [Order(100)] 
    public bool advancedDebugMode = false;

    // Declared at the BOTTOM of the script, but will be drawn FIRST in the Inspector!
    [Order(0)] 
    public string primaryHeader = "Main Settings";

    // Declared at the BOTTOM, but will be drawn SECOND
    [Order(1)]
    [BoxGroup("Data")]
    public Vector3 spawnPoint;
}

Performance Note

The sorting algorithm is executed dynamically during the OnGUI layout pass, but it is heavily optimized. It utilizes ListPool for temporary data collection and a cached static delegate for comparisons, resulting in 0 Bytes of GC Allocation per frame.