[2.0.15] Add create_asteroid() to LuaSpacePlatform

[redplasticstraw]

Essentially, add direct counterparts to spawn asteroids instead of asteroid chunks.

destroy_asteroids(area, position, name, limit, invert)
create_asteroids(asteroids)
find_asteroids_filtered(area, position, name, limit, invert)

[curiosity]

They are just entities.

[Bilka]

This already exists via getting the surface from the space platform and using the existing entity related methods.