[9.x] Fix implicitBinding and withTrashed route with child with no SoftDeletes trait

[stein-j]

This fixes an issue caused when using implicitBinding and withTrashed on a route and where the parent model has the SoftDelete trait and the child doesn't have the SoftDelete trait.

Ex:

class User extends Model
{
    use SoftDeletes;

    public function posts()
    {
        return $this->hasMany(Post::class);
    }

}

class Posts extends Model
{
    //
}

Route::scopeBindings()->get('users/{user}/posts/{post}', /*...*/)->withTrashed();

The following route call /users/1/posts/2 will throw this error Call to undefined method Illuminate\\Database\\Eloquent\\Relations\\HasMany::withTrashed().

---

This PR adds an extra check to verify if the child model instance has the SoftDeletes trait.

[BrandonSurowiec]

@taylorotwell Can this fix be backported to 8.x? The bug is present there as well.

[driesvints]

@BrandonSurowiec I think we can. Can you try a PR?

[BrandonSurowiec]

@driesvints Sure. Just won't get to it until the weekend. There are probably a few other PRs submitted to 9.x like the recent Http::retry() fix that could also be backported as a bug fix.

[driesvints]

@BrandonSurowiec Nothing is urgent : )