Update SnesColor constructor and add SnesTile tests

- Changed SnesColor constructor to remove constexpr, improving compatibility with non-constant expressions.
- Added new tests for SnesTile functionality, including unpacking, packing, and conversion between different bit depths.
- Enhanced TileInfo and Tile32 tests to verify construction, operations, and bit manipulation for better coverage.

src/app/gfx/snes_color.h

@@ -58,7 +58,7 @@ class SnesColor {
         snes_(ConvertRgbToSnes(val)),
         rom_color_(val) {}
 
-  constexpr SnesColor(uint8_t r, uint8_t g, uint8_t b) {
+  SnesColor(uint8_t r, uint8_t g, uint8_t b) {
     rgb_ = ImVec4(r, g, b, kColorByteMaxF);
     snes_color color;
     color.red = r;