Get/Set the number of worlds allocated up-front when the physics system starts.
Worlds are allocated as a single contiguous block, so a larger capacity uses more memory immediately and care must be taken.
When all worlds are in use, more are allocated on demand up to the supported maximum, so this is an initial capacity and not a hard limit.
Growing the array reallocates it, so set this to the number of worlds you expect in order to avoid reallocations during gameplay.
Setting this value to one reduces start-up memory usage to a minimum while still allowing more worlds to be created later.
The value must be in the range of 1 to 1024.
Any change will only be handled by Exiting Play mode in the Editor or restarting the player build.
A single PhysicsWorld.defaultWorld is automatically created therefore occupies one of the allocated worlds.
See PhysicsWorld.allocatedWorldCapacity for the number currently allocated, which can grow at runtime.