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
Gets rid of `orig_palette`, we now always have only 2 palettes:
1. `logical_palette`
This palette has color cycling / swapping applied but no global
effects such as brightness / fade-in.
2. `system_palette`
This palette is the actual palette used for rendering.
It is usually `logical_palette` with the global brightness setting
and fade-in/out applied.
Additionally, we now keep the k-d tree around and use it to
update single colors.
The colors that are color-cycled / swapped are never included
in the k-d tree, so the tree does not need updating on color
cycles/swaps.
Gleb Mazovetskiy
Anders Jenbo