Strict types support

[millnut]

With Drupal core moving towards strict types, more info I've added a test pipeline in preparation localgovdrupal/localgov_project#153 which has highlighted some failures which we should fix.

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  Line   modules/contrib/localgov_news/src/NewsExtraFieldDisplay.php                
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  167    Parameter #1 $form_object of static method                                 
         Drupal\localgov_news\NewsExtraFieldDisplay::articlePromotedStatus()        
         expects Drupal\node\NodeForm, Drupal\Core\Form\FormInterface given.        
  198    Parameter #2 $article of static method                                     
         Drupal\localgov_news\NewsExtraFieldDisplay::articleSetNewsroomPromote()    
         expects Drupal\node\NodeInterface, Drupal\Core\Entity\EntityInterface      
         given.                                                                     
  201    Parameter #2 $article of static method                                     
         Drupal\localgov_news\NewsExtraFieldDisplay::articleUnsetNewsroomPromote()  
         expects Drupal\node\NodeInterface, Drupal\Core\Entity\EntityInterface      
         given.                                                                     
  222    Call to function in_array() requires parameter #3 to be set.               
  253    Call to function array_search() requires parameter #3 to be set.           
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  Line   modules/contrib/localgov_news/tests/src/Functional/NewsPageTest.php  
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  185    Call to function in_array() requires parameter #3 to be set.         
  195    Call to function in_array() requires parameter #3 to be set.         
  211    Call to function in_array() requires parameter #3 to be set.         
  213    Call to function in_array() requires parameter #3 to be set.         
  215    Call to function in_array() requires parameter #3 to be set.         
  217    Call to function in_array() requires parameter #3 to be set.         
  232    Call to function in_array() requires parameter #3 to be set.         
  234    Call to function in_array() requires parameter #3 to be set.         
  236    Call to function in_array() requires parameter #3 to be set.         
  238    Call to function in_array() requires parameter #3 to be set.         
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