Make `action_on_strict_loading_violation` a module instance variable

Followup: https://github.com/rails/rails/pull/42442

activerecord/lib/active_record.rb

@@ -197,6 +197,13 @@ module ActiveRecord
   singleton_class.attr_accessor :application_record_class
   self.application_record_class = nil
 
+  ##
+  # :singleton-method:
+  # Set the application to log or raise when an association violates strict loading.
+  # Defaults to :raise.
+  singleton_class.attr_accessor :action_on_strict_loading_violation
+  self.action_on_strict_loading_violation = :raise
+
   def self.eager_load!
     super
     ActiveRecord::Locking.eager_load!

activerecord/lib/active_record/core.rb

@@ -127,12 +127,6 @@ module ActiveRecord
 
       class_attribute :belongs_to_required_by_default, instance_accessor: false
 
-      ##
-      # :singleton-method:
-      # Set the application to log or raise when an association violates strict loading.
-      # Defaults to :raise.
-      mattr_accessor :action_on_strict_loading_violation, instance_accessor: false, default: :raise
-
       class_attribute :strict_loading_by_default, instance_accessor: false, default: false
       class_attribute :strict_loading_mode, instance_accessor: true, default: :all
 
@@ -345,7 +339,7 @@ module ActiveRecord
       self.default_shard = :default
 
       def self.strict_loading_violation!(owner:, reflection:) # :nodoc:
-        case action_on_strict_loading_violation
+        case ActiveRecord.action_on_strict_loading_violation
         when :raise
           message = "`#{owner}` is marked for strict_loading. The `#{reflection.klass}` association named `:#{reflection.name}` cannot be lazily loaded."
           raise ActiveRecord::StrictLoadingViolationError.new(message)

activerecord/test/cases/strict_loading_test.rb

@@ -548,7 +548,7 @@ class StrictLoadingTest < ActiveRecord::TestCase
   end
 
   def test_strict_loading_violation_raises_by_default
-    assert_equal :raise, ActiveRecord::Base.action_on_strict_loading_violation
+    assert_equal :raise, ActiveRecord.action_on_strict_loading_violation
 
     developer = Developer.first
     assert_not_predicate developer, :strict_loading?
@@ -562,9 +562,9 @@ class StrictLoadingTest < ActiveRecord::TestCase
   end
 
   def test_strict_loading_violation_can_log_instead_of_raise
-    old_value = ActiveRecord::Base.action_on_strict_loading_violation
-    ActiveRecord::Base.action_on_strict_loading_violation = :log
-    assert_equal :log, ActiveRecord::Base.action_on_strict_loading_violation
+    old_value = ActiveRecord.action_on_strict_loading_violation
+    ActiveRecord.action_on_strict_loading_violation = :log
+    assert_equal :log, ActiveRecord.action_on_strict_loading_violation
 
     developer = Developer.first
     assert_not_predicate developer, :strict_loading?
@@ -576,7 +576,7 @@ class StrictLoadingTest < ActiveRecord::TestCase
       developer.audit_logs.to_a
     end
   ensure
-    ActiveRecord::Base.action_on_strict_loading_violation = old_value
+    ActiveRecord.action_on_strict_loading_violation = old_value
   end
 
   private