Use a classic pseudo-random hashing approach, by multiplication of chunk numbers
with large primes that should be more random.
- make slime density (as 1 in N) and maximum light level (default: no limit) configurable
- Allow using a 3d chunking system where y is also used for hashing
This does *not* modify spawn frequency, only the chunk logic.
Reviewed-on: VoxeLibre/VoxeLibre#4466
Reviewed-by: the-real-herowl <the-real-herowl@noreply.git.minetest.land>
Co-authored-by: kno10 <erich.schubert@gmail.com>
Co-committed-by: kno10 <erich.schubert@gmail.com>