Bring back Module::deserialize (#2858)

* Bring back `Module::deserialize`

I thought I was being clever suggesting that `Module::deserialize` was
removed from #2791 by funneling all module constructors into
`Module::new`. As our studious fuzzers have found, though, this means
that `Module::new` is not safe currently to pass arbitrary user-defined
input into. Now one might pretty reasonable expect to be able to do
that, however, being a WebAssembly engine and all. This PR as a result
separates the `deserialize` part of `Module::new` back into
`Module::deserialize`.

This means that binary blobs created with `Module::serialize` and
`Engine::precompile_module` will need to be passed to
`Module::deserialize` to "rehydrate" them back into a `Module`. This
restores the property that it should be safe to pass arbitrary input to
`Module::new` since it's always expected to be a wasm module. This also
means that fuzzing will no longer attempt to fuzz `Module::deserialize`
which isn't something we want to do anyway.

* Fix an example

* Mark `Module::deserialize` as `unsafe`

crates/c-api/include/wasmtime.h

@@ -992,9 +992,13 @@ WASM_API_EXTERN own wasmtime_error_t* wasmtime_module_serialize(
 
 /**
  * \brief Build a module from serialized data.
- * *
+ *
  * This function does not take ownership of any of its arguments, but the
  * returned error and module are owned by the caller.
+ *
+ * This function is not safe to receive arbitrary user input. See the Rust
+ * documentation for more information on what inputs are safe to pass in here
+ * (e.g. only that of #wasmtime_module_serialize)
  */
 WASM_API_EXTERN own wasmtime_error_t *wasmtime_module_deserialize(
     wasm_engine_t *engine,