Implement the remaining valid spec tests.

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.

lib/environ/src/lib.rs

@@ -48,10 +48,10 @@ mod vmoffsets;
 pub use compilation::{
     compile_module, Compilation, CompileError, RelocSink, Relocation, RelocationTarget, Relocations,
 };
-pub use module::{
-    DataInitializer, Export, MemoryPlan, MemoryStyle, Module, TableElements, TablePlan, TableStyle,
+pub use module::{Export, MemoryPlan, MemoryStyle, Module, TableElements, TablePlan, TableStyle};
+pub use module_environ::{
+    translate_signature, DataInitializer, ModuleEnvironment, ModuleTranslation,
 };
-pub use module_environ::{translate_signature, ModuleEnvironment, ModuleTranslation};
 pub use tunables::Tunables;
 pub use vmoffsets::VMOffsets;