Define attribute methods before attempting to populate records

`initialize_internals_callback` will attempt to assign attributes from
the current scope, which will fail if something defined the method
and calls super (meaning it won't hit `method_missing`).

Fixes #18339

activerecord/lib/active_record/core.rb

@@ -276,11 +276,11 @@ def table_metadata # :nodoc:
     #   User.new(first_name: 'Jamie')
     def initialize(attributes = nil, options = {})
       @attributes = self.class._default_attributes.dup
+      self.class.define_attribute_methods
 
       init_internals
       initialize_internals_callback
 
-      self.class.define_attribute_methods
       # +options+ argument is only needed to make protected_attributes gem easier to hook.
       # Remove it when we drop support to this gem.
       init_attributes(attributes, options) if attributes