Move entity_reference_create_field function to EntityReferenceTestTrait

Looks great! I just found two small problems:

1. +++ b/core/modules/entity_reference/src/Tests/EntityReferenceAdminTest.php
   @@ -19,6 +19,7 @@
   +  use EntityReferenceTestTrait;
   

   The trait is added here but its "add field" method is not used in the test :)

2. +++ b/core/modules/entity_reference/src/Tests/EntityReferenceTestTrait.php
   @@ -0,0 +1,70 @@
   +use Drupal\entity_reference\Tests\EntityReferenceTestTrait;
   

   This use statement is not needed.

Awesome! I grepped the codebase and entity_reference_create_field() is not used anywhere else, so we should be good to go here. Let's hope the testbot agrees.

Also updated the issue summary and added a beta evaluation.

Testbot was acting up, back to rtbc.

Straight reroll due to latest core breakage.

The reroll looks good.

+++ b/core/modules/entity_reference/src/Tests/EntityReferenceTestTrait.php
@@ -0,0 +1,69 @@
+  public function createEntityReferenceField($entity_type, $bundle, $field_name, $field_label, $target_entity_type, $selection_handler = 'default', $selection_handler_settings = array(), $cardinality = 1) {

Doesn't actually matter, but why is this public? Seems to be always called on $this->

For no good reason :P

Since entity_reference_create_field was only introduced in Drupal 8 I think it is okay to remove it. Also if contrib is using it already it really should not be - since fields should be created using CMI or using the Field and FieldStorage config entities directly.

Committed 60531a7 and pushed to 8.0.x. Thanks!