Update FlxPoint pivotRadians to proper order of operations

[MondayHopscotch]

Updates FlxPoint pivotRadians math which was calculating the rotation point improperly.
Fixes #2698

Old:

1. subtract point from pivot
2. apply rotation
3. add pivot to result
4. return

New:

1. subtract pivot from point
2. apply rotation
3. add pivot to result
4. return

I also updated the doc comments to specify "Counter-clockwise" as the use of cos and sin functions are counter-clockwise. Comparing behavior to the 4.11.0 branch, this is consistent with the behavior there despite that branch also specifying "clockwise"

[Geokureli]

@SeiferTim You mentioned in the discord that this doesn't fix #2698. It seems like there are multiple issues, here. to me this change makes sense but let me know what issues you're seeing, Tim

We're in a unique position here, anyone using the old p.rotate function will get a deprecation warning to use pivotDegrees, we can also use this to notify them of the new behavior, meaning this wouldn't be a breaking change, but I'd like to act fast, while people are still migrating to flixel 5

[Geokureli]

also, fun fact I broke this when deprecating rotate and created pivotDegrees. so this change is definitely a good idea

[Geokureli]

This seems to be working completely as I would expect, everything is good except it should say "clockwise" instead of "counter-clockwise"

Screen.Recording.2022-12-15.at.2.19.29.PM.mov

as for Tim's concern:

he problem with the old method was simply that no matter where point is in relation to pivot when you call pivot*, it treats it as if it's at 0 degrees from pivot first...

I'm simply not seeing it, as evident by the example above, for which I'll provide the source:

package states;

import flixel.FlxG;
import flixel.FlxSprite;
import flixel.math.FlxPoint;

class PivotTestState extends flixel.FlxState
{
    var sprite:FlxSprite;
    var pivot:FlxPoint;
    var p:FlxPoint;
    
    override function create()
    {
        super.create();
        
        p = FlxPoint.get(0, 50);
        pivot = FlxPoint.get(50, 50);
        
        trace('$p @ ${(p - pivot).degrees)}');
        for (i in 0...8)
        {
            p.pivotDegrees(pivot, 45);
            trace('$p @ ${(p - pivot).degrees)}');
        }
        /* output (beautified):
         * (x:   0.000 | y:  50.000 ) @  180
         * (x:  85.355 | y:  85.355 ) @ -135
         * (x:  50.000 | y:   0.000 ) @  -90
         * (x:  14.645 | y:  85.355 ) @  -45
         * (x: 100.000 | y:  50.000 ) @    0
         * (x:  14.645 | y:  14.645 ) @   45
         * (x:  50.000 | y: 100.000 ) @   90
         * (x:  85.355 | y:  14.645 ) @  135
         * (x:   0.000 | y:  50.000 ) @  180
        **/
        
        pivot.set(FlxG.width / 2, FlxG.height / 2);
        var pivotSprite = new FlxSprite().makeGraphic(6, 6, 0xFF0000ff);
        pivotSprite.x = pivot.x - pivotSprite.origin.x;
        pivotSprite.y = pivot.y - pivotSprite.origin.y;
        add(pivotSprite);
        
        p.set(pivot.x + 100, pivot.y);
        sprite = new FlxSprite().makeGraphic(50, 50, 0xFFff0000);
        sprite.x = p.x - sprite.origin.x;
        sprite.y = p.y - sprite.origin.y;
        add(sprite);
    }
    
    override function update(elapsed)
    {
        super.update(elapsed);
        
        p.pivotDegrees(pivot, 360 * elapsed);
        sprite.x = p.x - sprite.origin.x;
        sprite.y = p.y - sprite.origin.y;
    }
}