Allow object_id as a column name for ActiveRecord

Fixes rails#50160

The `object_id` name may be used by polymorphic relations where `object` is the best name, like `notification.object`.
In that case two columns are created: `object_id` and `object_type`.

Update tests and comments to reference `__id__` instead of `object_id` for consistency.

activerecord/lib/active_record/associations.rb

@@ -1163,7 +1163,7 @@ def association_instance_set(name, association)
       #
       #    d = Dungeon.first
       #    t = d.traps.first
-      #    d.object_id == t.dungeon.object_id # => true
+      #    d.__id__ == t.dungeon.__id__ # => true
       #
       # The +Dungeon+ instances +d+ and <tt>t.dungeon</tt> in the above example refer to
       # the same in-memory instance since the association matches the name of the class.

activerecord/lib/active_record/attribute_methods.rb

@@ -33,7 +33,7 @@ def dangerous_attribute_methods # :nodoc:
           Base.private_instance_methods -
           Base.superclass.instance_methods -
           Base.superclass.private_instance_methods +
-          %i[__id__ dup freeze frozen? hash object_id class clone]
+          %i[__id__ dup freeze frozen? hash class clone]
         ).map { |m| -m.to_s }.to_set.freeze
       end
     end

activerecord/lib/active_record/core.rb

@@ -488,10 +488,10 @@ def init_with_attributes(attributes, new_record = false) # :nodoc:
     #   new_user.name = "Joe"
     #   user.name               # => "Joe"
     #
-    #   user.object_id == new_user.object_id            # => false
-    #   user.name.object_id == new_user.name.object_id  # => true
+    #   user.__id__ == new_user.__id__            # => false
+    #   user.name.__id__ == new_user.name.__id__  # => true
     #
-    #   user.name.object_id == user.dup.name.object_id  # => false
+    #   user.name.__id__ == user.dup.name.__id__  # => false
 
     ##
     # :method: dup

activerecord/test/cases/associations_test.rb

@@ -1261,7 +1261,7 @@ def test_preload_with_available_records_with_through_association
     end
 
     assert_predicate author.association(:essay_category), :loaded?
-    assert categories.map(&:object_id).include?(author.essay_category.object_id)
+    assert categories.map(&:__id__).include?(author.essay_category.__id__)
   end
 
   def test_preload_with_only_some_records_available_with_through_associations
@@ -1307,7 +1307,7 @@ def test_preload_with_available_records_queries_when_scoped
     end
 
     assert_predicate post.association(:author), :loaded?
-    assert_not_equal david.object_id, post.author.object_id
+    assert_not_equal david.__id__, post.author.__id__
   end
 
   def test_preload_with_available_records_queries_when_collection
@@ -1319,7 +1319,7 @@ def test_preload_with_available_records_queries_when_collection
     end
 
     assert_predicate post.association(:comments), :loaded?
-    assert_empty post.comments.map(&:object_id) & comments.map(&:object_id)
+    assert_empty post.comments.map(&:__id__) & comments.map(&:__id__)
   end
 
   def test_preload_with_available_records_queries_when_incomplete