Major performance optimizations and bug fixes

• Fixed an issue that reset the resolution setting upon re-entering the main menu.
• Game data is now loaded only once per session (previously it occurred every time you enter the main menu).
• Biome enemies (slimes) now spawn at different times in different biomes, which prevents screen freezes at spawn times.
• Reduced the size of a single biome segment. Reduced the number of biome segments loaded into the game at a time.
• There is now a limit to how many flowers and enemies a biome segment can hold at a time, resulting in a major performance improvement in the later parts of a run.
• Bigger (and slower) enemies now react to the player a bit faster. Faster enemies are now much harder to evade.