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

Cargo.lock

@@ -2166,7 +2166,6 @@ dependencies = [
  "log",
  "wasmtime",
  "wasmtime-fuzzing",
- "wasmtime-jit",
 ]
 
 [[package]]
@@ -2181,8 +2180,6 @@ dependencies = [
  "wasmparser 0.47.0",
  "wasmprinter",
  "wasmtime",
- "wasmtime-environ",
- "wasmtime-jit",
  "wat",
 ]