Support for SIMD operations for RGG1555

Description

Up to 3x the performance for RGG1555 with SIMD operations. The current implementation is hardcoded for 16 bytes at a time (128 bits). Still requires some testing and validation for AVX2 and AVX512.

Fixes #45 (closed)

benches/color.rs

-use boytacean::ppu::Ppu;
+use boytacean::color::rgb888_to_rgb1555_scalar;
+
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
 
 fn multiply_array_size<T: Clone>(arr: &[T], multiplier: usize) -> Vec<T> {
@@ -17,7 +18,7 @@ fn benchmark_rgb_conversion(c: &mut Criterion) {
 
     c.bench_function("rgb888_to_rgb1555_scalar", |b| {
         b.iter(|| {
-            Ppu::rgb888_to_rgb1555_scalar(
+            rgb888_to_rgb1555_scalar(
                 black_box(&rgb888_pixels_sized),
                 black_box(&mut rgb1555_pixels),
             )
@@ -26,9 +27,10 @@ fn benchmark_rgb_conversion(c: &mut Criterion) {
 
     #[cfg(feature = "simd")]
     {
+        use boytacean::color::rgb888_to_rgb1555_simd;
         c.bench_function("rgb888_to_rgb1555_simd", |b| {
             b.iter(|| {
-                Ppu::rgb888_to_rgb1555_simd(
+                rgb888_to_rgb1555_simd(
                     black_box(&rgb888_pixels_sized),
                     black_box(&mut rgb1555_pixels),
                 )