And lots of other miscellaneous changes. Rename InstanceWorld to InstancePlus and reorganize its contents. This still isn't a great name, but at least now it has a clear purpose.
This is the wasmtime-environ crate, which contains the implementations
of the ModuleEnvironment and FuncEnvironment traits from
cranelift-wasm. They effectively
implement an ABI for basic wasm compilation, which can be used for JITing,
native object files, or other purposes.