FlxSprite: Allow changes to cliprect to take effect without setter

[Geokureli]

Fixes #3162

Will probably break clipRect unit tests

This is part of a larger effort, to add slice rects to FlxSprites so there's semi-unrelated changes like:

• Moves logic from drawComplex to drawFrameComplex (will eventually replace it)
• Add FlxFrame.clip to eventually replace the badly named clipTo, also optimizes some of the logic in them

package states;

import flixel.FlxG;
import flixel.FlxSprite;
import flixel.math.FlxRect;
import openfl.geom.Rectangle;

class ClipRectRoundTestState extends flixel.FlxState
{
    var sprite:FlxSprite;
    
    override function create()
    {
        super.create();
        
        sprite = new FlxSprite(10, 10);
        sprite.makeGraphic(100, 100);
        sprite.graphic.bitmap.fillRect(new Rectangle(20, 20, 60, 60), 0xFF0000ff);
        sprite.graphic.bitmap.fillRect(new Rectangle(40, 40, 20, 20), 0xFFffffff);
        add(sprite);
        sprite.clipRect = FlxRect.get(10, 10, 80, 80);
    }
    
    override function update(elapsed)
    {
        super.update(elapsed);
        
        sprite.clipRect.x += (FlxG.keys.pressed.D ? 1.0 : 0.0) - (FlxG.keys.pressed.A ? 1.0 : 0.0);
        sprite.clipRect.y += (FlxG.keys.pressed.S ? 1.0 : 0.0) - (FlxG.keys.pressed.W ? 1.0 : 0.0);
        
        sprite.clipRect.width += (FlxG.keys.pressed.RIGHT ? 1.0 : 0.0) - (FlxG.keys.pressed.LEFT ? 1.0 : 0.0);
        sprite.clipRect.height += (FlxG.keys.pressed.DOWN  ? 1.0 : 0.0) - (FlxG.keys.pressed.UP   ? 1.0 : 0.0);
    }
}

Screen.Recording.2025-02-27.at.9.46.36.AM.mov

TODO

• unit tests don't know how to test graphical things
• test flash manually