provide in-memory world implementation (MapWorldProvider)

[keturn]

While converting some tests from WorldProvidingHeadlessEnvironment to ModuleTestingEnvironment, I discovered that WPHE uses MapWorldProvider, which generates chunks on demand.

There might be a handful of modules providing large-scale features that need to deal with the intricacies of chunk loading, and they should be able to use the default WorldProvider so they don't get a false sense of security. But I think most tests for most modules are only interested a small area, and this on-demand behavior would make things much easier for them. It would eliminate the need for them to use things like forceAndWaitForGeneration.

[keturn]

The WorldProvider is set during a step in the loading process, InitialiseWorld.

I don't see a quick way to have MTE override that particular detail.