Add more palette blending benchmarks

Adds separate benchmarks for building the tree vs lookup

    BM_GenerateBlendedLookupTable    2247062 ns      2246554 ns          312
    BM_BuildTree                        6842 ns         6840 ns       102200
    BM_FindNearestNeighbor        2535103632 ns   2534784320 ns            1 items_per_second=6.61879M/s

test/palette_blending_benchmark.cpp

@@ -1,10 +1,13 @@
 #include "utils/palette_blending.hpp"
 
 #include <array>
+#include <cstdint>
 
 #include <SDL.h>
 #include <benchmark/benchmark.h>
 
+#include "utils/palette_kd_tree.hpp"
+
 namespace devilution {
 
 std::array<SDL_Color, 256> logical_palette;
@@ -36,7 +39,42 @@ void BM_GenerateBlendedLookupTable(benchmark::State &state)
 	}
 }
 
+void BM_BuildTree(benchmark::State &state)
+{
+	SDL_Color *palette = logical_palette.data();
+	GeneratePalette(palette);
+
+	for (auto _ : state) {
+		PaletteKdTree tree(palette, -1, -1);
+		benchmark::DoNotOptimize(tree);
+	}
+}
+
+void BM_FindNearestNeighbor(benchmark::State &state)
+{
+	SDL_Color *palette = logical_palette.data();
+	GeneratePalette(palette);
+	PaletteKdTree tree(palette, -1, -1);
+
+	std::vector<std::array<uint8_t, 3>> queries;
+	int64_t itemsProcessed = 0;
+	for (auto _ : state) {
+		for (int r = 0; r < 256; ++r) {
+			for (int g = 0; g < 256; ++g) {
+				for (int b = 0; b < 256; ++b) {
+					uint8_t result = tree.findNearestNeighbor({ static_cast<uint8_t>(r), static_cast<uint8_t>(g), static_cast<uint8_t>(b) });
+					benchmark::DoNotOptimize(result);
+				}
+			}
+		}
+		itemsProcessed += 256 * 256 * 256;
+	}
+	state.SetItemsProcessed(itemsProcessed);
+}
+
 BENCHMARK(BM_GenerateBlendedLookupTable);
+BENCHMARK(BM_BuildTree);
+BENCHMARK(BM_FindNearestNeighbor);
 
 } // namespace
 } // namespace devilution