DateTimeFormat: support quick access properties

[h4kuna]

• new feature? yes
• BC break? no
• doc PR: nette/docs#??? if you agree with theses changes I will write.

I add trait DateTimeFormat what extends class DateTime, with quick access to frequent date and time values with right type.

I used SmartObject and added read-only properties for DateTime.

Example

use Nette\Utils\DateTime;

$now = new DateTime('2023-09-13');
dump($now->year === 2023); // true
dump($now->year === '2023'); // false, 2023 is string
dump($now->month === 9);
dump($now->day === 13);

[h4kuna]

If you don't like it, let's close it.