Add missing autoload Type (#31123)

Attribute modules (`Attribute`, `Attributes`, `AttributeSet`) uses
`Type`, but referencing `Type` before the modules still fail.

```
% ./bin/test -w test/cases/attribute_test.rb -n test_with_value_from_user_validates_the_value
Run options: -n test_with_value_from_user_validates_the_value --seed 31876

E

Error:
ActiveModel::AttributeTest#test_with_value_from_user_validates_the_value:
NameError: uninitialized constant ActiveModel::AttributeTest::Type
    /Users/kamipo/src/github.com/rails/rails/activemodel/test/cases/attribute_test.rb:233:in `block in <class:AttributeTest>'

bin/test test/cases/attribute_test.rb:232

Finished in 0.002985s, 335.0479 runs/s, 335.0479 assertions/s.
1 runs, 1 assertions, 0 failures, 1 errors, 0 skips
```

Probably we need more autoloading at least `Type`.

activemodel/lib/active_model.rb

@@ -47,6 +47,7 @@ module ActiveModel
   autoload :SecurePassword
   autoload :Serialization
   autoload :Translation
+  autoload :Type
   autoload :Validations
   autoload :Validator
 

activemodel/lib/active_model/attribute.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/object/duplicable"
-require "active_model/type"
 
 module ActiveModel
   class Attribute # :nodoc:

activemodel/lib/active_model/attributes.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/object/deep_dup"
-require "active_model/type"
 require "active_model/attribute_set"
 require "active_model/attribute/user_provided_default"
 

activemodel/test/cases/attribute_set_test.rb

@@ -2,7 +2,6 @@
 
 require "cases/helper"
 require "active_model/attribute_set"
-require "active_model/type"
 
 module ActiveModel
   class AttributeSetTest < ActiveModel::TestCase

activemodel/test/cases/type/big_integer_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/binary_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/boolean_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/date_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/date_time_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/decimal_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/float_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/immutable_string_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/integer_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 require "active_support/core_ext/numeric/time"
 
 module ActiveModel

activemodel/test/cases/type/registry_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/string_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/time_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activemodel/test/cases/type/value_test.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type

activerecord/lib/active_record.rb

@@ -104,6 +104,7 @@ module ActiveRecord
 
     autoload :Result
     autoload :TableMetadata
+    autoload :Type
   end
 
   module Coders

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require "active_record/type"
 require "active_record/connection_adapters/determine_if_preparable_visitor"
 require "active_record/connection_adapters/schema_cache"
 require "active_record/connection_adapters/sql_type_metadata"