feat!: improve afterError hook to accept array of functions, change to object args (#8389)

Changes the `afterError` hook structure, adds tests / more docs.
Ensures that the `req.responseHeaders` property is respected in the
error handler.

**Breaking**
`afterError` now accepts an array of functions instead of a single
function:
```diff
- afterError: () => {...}
+ afterError: [() => {...}]
```

The args are changed to accept an object with the following properties:
| Argument | Description |
| ------------------- |
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|
| **`error`** | The error that occurred. |
| **`context`** | Custom context passed between Hooks. [More
details](./context). |
| **`graphqlResult`** | The GraphQL result object, available if the hook
is executed within a GraphQL context. |
| **`req`** | The
[Request](https://developer.mozilla.org/en-US/docs/Web/API/Request)
object containing the currently authenticated `user` |
| **`collection`** | The [Collection](../configuration/collections) in
which this Hook is running against. This will be `undefined` if the hook
is executed from a non-collection endpoint or GraphQL. |
| **`result`** | The formatted error result object, available if the
hook is executed from a REST context. |