Ensure Trap is returned for start function traps (#768)

* Ensure `Trap` is returned for start function traps

Handle another case of errors coming out of instantiation, resolve a
FIXME, and remove an unneeded dependency from the wast testsuite crate.

* Run rustfmt

crates/api/src/trap.rs

@@ -74,7 +74,7 @@ impl fmt::Debug for UnsafeTrapInfo {
 
 /// A struct representing an aborted instruction execution, with a message
 /// indicating the cause.
-#[derive(Error, Debug)]
+#[derive(Error, Debug, Clone)]
 #[error("Wasm trap: {message}")]
 pub struct Trap {
     message: String,