[2.x] Keep only partial data in mergeProps

[vinnygambiny]

This PR resolve this issue inertiajs/inertia#2371

When you reload with partial data, the mergeProps dans deepMergeProps contains all props. So the VueJS will merge the prop with the response, but the response don't have the props.

Example props

[
    'user' => $user,
    'foo' => new MergeProp('foo value'),
]

If you reload with only user, the response will have mergeProps: ['foo'] but the foo is not there.

The same with the except.

[pascalbaljet]

Thanks!