## Description

Now that the BCS representation of an `Object` does not lose information
about whether it's a `MovePackage` or `MoveObject`, it becomes possible
to implement `asMoveObject`, which this PR does.

## Test Plan

Manually tested with GraphiQL:


![image](https://github.com/MystenLabs/sui/assets/332275/0ea58cf7-21dc-4177-9b3f-84ee56e110f2)


## Stack

- #14376 
- #14377