Lua get_biome_data: calc heat and humidity only once

[kno10]

At every call to l_get_biome_data(), the lua API for getting the biome at a position, heat and humidity are computed twice: once inside calcBiomeAtPoint, and then again below to return exact heat and humidity.

Because of the perlin noises, this function is fairly expensive, and shows up in flamegraphs.

See, e.g., https://codeberg.org/mineclonia/mineclonia/pulls/2681#issuecomment-2650068

have you any idea whether it is possible to cache the results of biome tests (core.get_biome_data) when it is likely to be called repetitively with closely adjacent positions? core.get_biome_data is suboptimal and evaluates biome noise four times per call, and currently occupies multiple milliseconds of a globalstep with thousands of loaded Minecraft chunks.

Computing them once each is enough. It makes the function roughly twice as fast (well, there is also a y blending noise additionally, it could potentially even be left out. For example with the valley mapgen, biomes are not exact anyway.

[appgurueu]

I haven't tested, but this looks fine as-is and I don't think testing should be necessary.