[7.x] Check a request header with an array value

[pkboom]

This PR enables to check if a request has a header with a value of an array. Currently, if a header has a value of an array, it cannot be verified. For example,

Http::withHeaders([
    'X-Foo'  => ['Bar', 'Baz'],
])->get('/');

Http::assertSent(function ($request) {
    return $request->hasHeader('X-Foo', ['Bar', 'Baz']); => false
});

This PR will enable to verify header values inside an array.

 $request->hasHeader('X-Foo', ['Bar', 'Baz']); => true.
 $request->hasHeader('X-Foo', 'Bar'); => true.
 $request->hasHeader('X-Foo', ['Bar']); => true.