Fix fuzzer expectation about valid modules

Recent changes to fuzzers made expectations more strict about handling
errors while fuzzing, but this erroneously changed a module compilation
step to always assume that the input wasm is valid. Instead a flag is
now passed through indicating whether the wasm blob is known valid or
invalid, and only if compilation fails and it's known valid do we panic.

fuzz/fuzz_targets/instantiate-maybe-invalid.rs

@@ -9,6 +9,7 @@ use wasmtime_fuzzing::oracles;
 fuzz_target!(|module: MaybeInvalidModule| {
     oracles::instantiate_with_config(
         &module.to_bytes(),
+        false,
         wasmtime_fuzzing::fuzz_default_config(Strategy::Auto).unwrap(),
         Some(Duration::from_secs(20)),
     );