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/lib.rs

@@ -26,6 +26,7 @@ mod code_memory;
 mod compiler;
 mod context;
 mod function_table;
+mod imports;
 mod instantiate;
 mod link;
 mod namespace;