Refactor rendering architecture and replace rasterizer with renderer

- Introduced SoftwareRenderer as a pixel-accurate software rendering backend.
- Removed the obsolete wolf_3d_rasterizer.dart file.
- Created a new wolf_3d_renderer.dart file to centralize rendering exports.
- Updated tests to accommodate the new rendering structure, including pushwall and projection sampling tests.
- Modified the WolfAsciiRenderer and WolfFlutterRenderer to utilize the new SoftwareRenderer.
- Enhanced enemy spawn tests to include new enemy states.

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

packages/wolf_3d_dart/test/rasterizer/projection_sampling_test.dart

@@ -1,5 +1,5 @@
 import 'package:test/test.dart';
-import 'package:wolf_3d_dart/src/rasterizer/rasterizer.dart';
+import 'package:wolf_3d_dart/src/rendering/renderer_backend.dart';
 import 'package:wolf_3d_dart/wolf_3d_data_types.dart';
 import 'package:wolf_3d_dart/wolf_3d_engine.dart';
 
@@ -28,7 +28,7 @@ void main() {
   });
 }
 
-class _TestRasterizer extends Rasterizer<FrameBuffer> {
+class _TestRasterizer extends RendererBackend<FrameBuffer> {
   _TestRasterizer({required this.customProjectionViewHeight});
 
   final int customProjectionViewHeight;

packages/wolf_3d_dart/test/rasterizer/pushwall_rasterizer_test.dart

@@ -4,7 +4,7 @@ import 'package:test/test.dart';
 import 'package:wolf_3d_dart/wolf_3d_data_types.dart';
 import 'package:wolf_3d_dart/wolf_3d_engine.dart';
 import 'package:wolf_3d_dart/wolf_3d_input.dart';
-import 'package:wolf_3d_dart/wolf_3d_rasterizer.dart';
+import 'package:wolf_3d_dart/wolf_3d_renderer.dart';
 
 void main() {
   group('Pushwall rasterization', () {
@@ -64,7 +64,7 @@ void main() {
         ..offset = 0.5;
       engine.pushwallManager.activePushwall = pushwall;
 
-      final frame = SoftwareRasterizer().render(engine);
+      final frame = SoftwareRenderer().render(engine);
       final centerIndex =
           (frame.height ~/ 2) * frame.width + (frame.width ~/ 2);