[6.x] Fix testing with unencrypted cookies

[gentcys]

This PR provide a way to specify cookies will not be encrypted before sending with the request.

$this->withCookie('bar', 'qux')
     ->withUnencryptedCookie('foo', 'bar')
     ->get('/');

$this->withCookies($cookies) // cookies will be encrypted
     ->withUnencryptedCookies($unencryptedCookies) // cookies will not be encrypted
     ->get('/');

Fixes #31282

[taylorotwell]

This feels like a pretty big breaking change to make withCookies no longer encrypted? Why not make the method withUnencryptedCookie so we don't have to have that breaking change?

[gentcys]

@taylorotwell It's a great idea.