Remove usage of deprecated entity.manager service

Please review this.

Hey @deepak, if you search for entity_type.manager you'll see that it is used in at least 4 other places, you'll need to clean those up and anything that depends on them.

There is no work to be done here, for now.

In \Drupal\commerce_pos\POS it is passing the deprecated manager because it has to.

May as well postpone as all usage is required by core.

We're back at active, because 8.6.x HEAD now has committed a change to the ContentEntityForm to remove the deprecated service.

#2894261: Deprecated service entity.manager needs to be replaced with entity_type.manager in ContentEntityForm

Needs a reroll

Now change the POSForm constructor.

Not running tests and setting to NW because not user what to do with this usage of $entity_manager, which was added in 2950975-#9

    // This is a hack around what I think is a php bug, at least in 7.1.15
    // The logStorage static can lose reference to the entityType object sometimes.
    $this->logStorage = clone $entity_manager->getStorage('commerce_log');