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_subsites/localgov_subsites.module    
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  132    Call to function in_array() requires parameter #3 to be set.  
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  Line   modules/contrib/localgov_subsites/src/Plugin/Block/SubsitesHierarchyTrait.php  
         (in context of class                                                           
         Drupal\localgov_subsites\Plugin\Block\SubsitesAbstractBlockBase)               
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  113    Call to function in_array() requires parameter #3 to be set.                   
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  Line   modules/contrib/localgov_subsites/src/Plugin/Block/SubsitesHierarchyTrait.php  
         (in context of class Drupal\localgov_subsites\Subsite)                         
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  113    Call to function in_array() requires parameter #3 to be set.                   
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  Line   modules/contrib/localgov_subsites/src/Plugin/Block/SubsitesNavigationBlock.php  
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  126    Call to function in_array() requires parameter #3 to be set.                    
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