feat: add toBeAscending, toBeDescending, and toBeSorted expectations

[sonalidudhia]

Adds three new array sorting expectations.

Useful for testing query results, pagination, leaderboards, and sorted collections.

expect([1, 2, 3])->toBeAscending();
expect([3, 2, 1])->toBeDescending();
expect([1, 2, 2, 3])->toBeAscending(); // equal adjacent OK

expect($users)->toBeSorted(by: 'age');
expect($users)->toBeSorted(by: 'age', direction: 'desc');
expect($posts)->toBeSorted(by: 'created_at'); // works with DateTime

// Object properties
$users = [
    (object)['name' => 'Anna'],
    (object)['name' => 'Ben'],
];
expect($users)->toBeSorted(by: 'name');

// Negation
expect([3, 1, 2])->not->toBeAscending();