@cubejs-client/core load method error does not contain HTTP error code

**Describe the bug**
In `@cubejs-client/core`, when an errors occurs, there is no way to get errors the HTTP error code.

**To Reproduce**
1. Make a request using `@cubejs-client/core` like this
```
const makeQuery = async () => {
const cubejsApi = cubejs(
'CUBEJS-API-TOKEN',
{ apiUrl: 'http://localhost:4000/cubejs-api/v1' }
);

try {
const response = await cubejsApi.load(query);
return response.chartPivot();
} catch (error) {
console.log(error);
}
}
```
2. `error` in the `catch` block does not contain http error code

**Expected behavior**
`error` should contain the HTTP error code

**Version:**
`^0.15.4`

**Additional context**
-