Replaced \Drupal::entityManager() in Kernel and Web tests

Problem/Motivation

The EntityManager is @deprecated, and there are lots of usages of \Drupal::entityManager() in core.

Proposed resolution

As a step to remove usages, but keep things manageable,

-   \Drupal::entityManager()->foo();
+  $this->container->get('the_proper_entity_service.manager')->foo();

just in *Test.php, which is about ~230 usages, but only comprising a handful of patterns.

Remaining tasks

TBD.

User interface changes

None.

API changes

None.

Data model changes

None.

Original Report

Replaced with \Drupal::entityTypeManager() instead of \Drupal::entityManager() in date time.