fix: Fix creating error out of object (#784)

## Description

Partially fixes problems of #783 with uninformative error

### Introduces a breaking change?

- [ ] Yes
- [x] No

### Type of change

- [x] Bug fix (change which fixes an issue)
- [ ] New feature (change which adds functionality)
- [ ] Documentation update (improves or adds clarity to existing
documentation)
- [ ] Other (chores, tests, code style improvements etc.)

### Tested on

- [x] iOS
- [ ] Android

### Testing instructions

Run code as in #783 described. Then apply fix and check if the error
message is now created correctly.

### Screenshots

<!-- Add screenshots here, if applicable -->

### Related issues

<!-- Link related issues here using #issue-number -->

### Checklist

- [x] I have performed a self-review of my code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have updated the documentation accordingly
- [x] My changes generate no new warnings

### Additional notes

<!-- Include any additional information, assumptions, or context that
reviewers might need to understand this PR. -->

Author: msluszniak

packages/react-native-executorch/src/errors/errorUtils.ts

@@ -1,5 +1,18 @@
 import { RnExecutorchErrorCode } from './ErrorCodes';
 
+function isRnExecutorchError(
+  e: unknown
+): e is { code: number; message: string } {
+  return (
+    typeof e === 'object' &&
+    e !== null &&
+    'code' in e &&
+    'message' in e &&
+    typeof (e as RnExecutorchError).code === 'number' &&
+    typeof (e as RnExecutorchError).message === 'string'
+  );
+}
+
 export class RnExecutorchError extends Error {
   public code: RnExecutorchErrorCode;
   public cause?: unknown;
@@ -13,6 +26,10 @@ export class RnExecutorchError extends Error {
 }
 
 export function parseUnknownError(e: unknown): RnExecutorchError {
+  if (isRnExecutorchError(e)) {
+    return new RnExecutorchError(e.code, e.message);
+  }
+
   if (e instanceof RnExecutorchError) {
     return e;
   }