[2.0.9] Add missing strict_types=1 diretcives

Done. It is a risky change? What do we need to check?

Do we also apply this rules to the tests?

Hello,

TODO:
- Add Gitlab CI task to execute PHPCS Fixer

Let's use the same standards across UI Suite.

This is what I use to stick to PHPCS requirements + a few things not covered by PHP CS:
- "drupol/phpcsfixer-configs-drupal": "^2.2",
- https://gitlab.com/florenttorregrosa-drupal/docker-drupal-project/-/blob...

It is a risky change? What do we need to check?

it is a risky change !!! For example, i have now this issue:

Uncaught PHP Exception TypeError: "Drupal\ui_patterns\Element\ComponentFormBase::getSources(): Argument #1 ($prop_or_slot_id) must be of type string, int given, called in web/modules/custom/ui_patterns/src/Element/ComponentSlotForm.php on line 284" at web/modules/custom/ui_patterns/src/Element/ComponentFormBase.php line 170