Move event errors to respective usage

Author: arjunr2

crates/wasmtime/src/runtime/rr/core/events/common_events.rs

@@ -28,3 +28,7 @@ impl Validate<&Result<RRFuncArgVals>> for WasmFuncReturnEvent {
         self.0.validate(*expect)
     }
 }
+
+event_error_types! {
+    pub struct WasmFuncReturnError(..)
+}