Problem/Motivation
As per #2976394: Investigate problems with Symfony 4 now , various things are failing with this deprecation:
1x: The "Drupal\Component\DependencyInjection\Container" class implements "Symfony\Component\DependencyInjection\ResettableContainerInterface" that is deprecated since Symfony 4.2, use "Symfony\Contracts\Service\ResetInterface" instead.
1x in EntityAccessCheckTest::setUp from Drupal\Tests\Core\Entity
Unfortunately Symfony\Contracts\Service\ResetInterface does not exist in Symfony 3.4, so we cannot directly use that yet. Looks like we need to put this on an ignore list, introduce a ResetInterface of our own until we depend on Symfony 4 or stop implementing ResettableContainerInterface. If we add our own ResetInterface, then people may start to typehint/depend on that which would be an unintended side effect though.
Proposed resolution
Stop using ResettableContainerInterface in Drupal\Component\DependencyInjection\Container. Keep the method's implementation.
Remaining tasks
Commit.
User interface changes
None.
API changes
ResettableContainerInterface in no longer used on Drupal\Component\DependencyInjection\Container. The reset() method is kept though. Code type-hinting on ResettableContainerInterface will break. We did not find contrib modules that type-hinted on it.
Data model changes
None.
Release notes snippet
N/A
