FlxPathfinder - Overhaul to pathfinding

[Geokureli]

I moved all of the pathfinding logic to a new class, so that it can be extended with different algorithms
Excerpt from FlxPathfinder docs:

Used to find paths in a FlxBaseTilemap. extend this class and override
getNeighbors and getDistance to create you're own! For top-down maps, it may
be wiser to extend FlxDiagonalPathfinder, as it already has a lot of basic helpers.

To use, either call myPathfinder.findPath(myMap, start, end) or
myMap.findPathCustom(myPathfinder, start, end)

I plan to add a platformer pathfinder, too, but that doesn't need to be included here.

No breaking changes, just more ways to execute pathfinding. Im open to ideas for unit tests, I'll try to think of some.

[Geokureli]

New features:

• FlxCollision: Added calcRectEntry and calcRectExit (#2480)
• FlxTilemap: Overhaul to pathfinding (#2480)
  • FlxPathfinder: Allows customizable pathfinding algorithms for tilemap
  • FlxPathSimplifier: Replace findPath simplify args with a new enum
  • Expose previously private fields: tileWidth, tileHeight, scaledTileWidth, scaledTileHeight, scaledWidth, and scaledHeight
  • FlxBaseTilemap: added calcRayEntry and calcRayExit
• FlxPath: added immovable bool (previously object were always immovable when following paths) (#2480)
• FlxPathDrawData: added myFlxPath.debugDrawData to allow custom colors and draw properties (#2480)
• FlxDirectionFlags: added fromBools static helper (#2480)
• FlxAxes: added x and y getters and NONE value (#2480)

Changes and improvements:

• FlxTilemap: Renamed ray to rayStep added new ray with no resolution arg (#2480)
• FlxPath: move to flixel.path.FlxPath (#2480)