Move compilation into Module from Instance. (#822)

* Move compilation into Module from Instance.

* Fix fuzzing

* Use wasmtime::Module in fuzzing crates

Instead of wasmtime_jit.

* Compile eagerly.

* Review fixes.

* Always use the saved name.

* Preserve the former behavior for fuzzing oracle

crates/jit/src/context.rs

@@ -156,7 +156,6 @@ impl Context {
             &mut *self.compiler,
             data,
             None,
-            &mut self.namespace,
             Rc::clone(&self.global_exports),
             debug_info,
         )