[5.7] Check for model in assertViewHas

[FatBoyXPC]

When using assertViewHas with a model it can end up comparing class state that the test may not care about, such as wasRecentlyCreated, pivots, or relationships, etc. The way I currently go about this is by passing a callback to assertviewHas:

$this->assertViewHas('user', function ($model) use ($user) {
    return $user->is($model);
});

I think being able to instead call it with assertViewHas('user', $user) would be a nice change, and I don't see any obvious negative consequences to this (unless the user cared about the 'hidden' state).

I'm not too cracked up about the test I added as it requires internal knowledge of $response, but I figure it's better than adding no tests. I could get rid of this line, but it would require rewriting assertViewHas to not be reliant on __get.

Edit: I have a couple custom assertions I would like to PR. They are related to each other, but not to this one - should I submit it as a separate PR or make it part of this one?