PERF: 15% faster attribute access

Delegating to just one line method is to not be worth it.
Avoiding the delegation makes `read_attribute` about 15% faster.

```ruby
ActiveRecord::Schema.define do
  create_table :users, force: true do |t|
    t.string :name
  end
end

class User < ActiveRecord::Base
  def fast_read_attribute(attr_name, &block)
    name = attr_name.to_s
    name = self.class.attribute_aliases[name] || name

    name = @primary_key if name == "id" && @primary_key
    @attributes.fetch_value(name, &block)
  end
end

user = User.create!(name: "user name")

Benchmark.ips do |x|
  x.report("read_attribute('id')") { user.read_attribute('id') }
  x.report("read_attribute('name')") { user.read_attribute('name') }
  x.report("fast_read_attribute('id')") { user.fast_read_attribute('id') }
  x.report("fast_read_attribute('name')") { user.fast_read_attribute('name') }
end
```

```
Warming up --------------------------------------
read_attribute('id')   165.744k i/100ms
read_attribute('name')
                       162.229k i/100ms
fast_read_attribute('id')
                       192.543k i/100ms
fast_read_attribute('name')
                       191.209k i/100ms
Calculating -------------------------------------
read_attribute('id')      1.648M (± 1.7%) i/s -      8.287M in   5.030170s
read_attribute('name')
                          1.636M (± 3.9%) i/s -      8.274M in   5.065356s
fast_read_attribute('id')
                          1.918M (± 1.8%) i/s -      9.627M in   5.021271s
fast_read_attribute('name')
                          1.928M (± 0.9%) i/s -      9.752M in   5.058820s
```

activemodel/lib/active_model/attribute_set.rb

@@ -48,10 +48,12 @@ module ActiveModel
     def write_from_user(name, value)
       raise FrozenError, "can't modify frozen attributes" if frozen?
       attributes[name] = self[name].with_value_from_user(value)
+      value
     end
 
     def write_cast_value(name, value)
       attributes[name] = self[name].with_cast_value(value)
+      value
     end
 
     def freeze

activemodel/lib/active_model/attributes.rb

@@ -48,7 +48,7 @@ module ActiveModel
           ) do |temp_method_name, attr_name_expr|
             owner <<
               "def #{temp_method_name}(value)" <<
-              "  write_attribute(#{attr_name_expr}, value)" <<
+              "  _write_attribute(#{attr_name_expr}, value)" <<
               "end"
           end
         end
@@ -124,12 +124,11 @@ module ActiveModel
         name = attr_name.to_s
         name = self.class.attribute_aliases[name] || name
 
-        _write_attribute(name, value)
+        @attributes.write_from_user(name, value)
       end
 
       def _write_attribute(attr_name, value)
         @attributes.write_from_user(attr_name, value)
-        value
       end
       alias :attribute= :_write_attribute
 
@@ -137,12 +136,11 @@ module ActiveModel
         name = attr_name.to_s
         name = self.class.attribute_aliases[name] || name
 
-        _read_attribute(name)
+        @attributes.fetch_value(name)
       end
 
-      def _read_attribute(attr_name)
+      def attribute(attr_name)
         @attributes.fetch_value(attr_name)
       end
-      alias :attribute :_read_attribute
   end
 end

activerecord/lib/active_record/attribute_methods.rb

@@ -182,7 +182,7 @@ module ActiveRecord
       def has_attribute?(attr_name)
         attr_name = attr_name.to_s
         attr_name = attribute_aliases[attr_name] || attr_name
-        _has_attribute?(attr_name)
+        attribute_types.key?(attr_name)
       end
 
       def _has_attribute?(attr_name) # :nodoc:
@@ -256,7 +256,7 @@ module ActiveRecord
     def has_attribute?(attr_name)
       attr_name = attr_name.to_s
       attr_name = self.class.attribute_aliases[attr_name] || attr_name
-      _has_attribute?(attr_name)
+      @attributes.key?(attr_name)
     end
 
     def _has_attribute?(attr_name) # :nodoc:

activerecord/lib/active_record/attribute_methods/read.rb

@@ -27,7 +27,7 @@ module ActiveRecord
         name = self.class.attribute_aliases[name] || name
 
         name = @primary_key if name == "id" && @primary_key
-        _read_attribute(name, &block)
+        @attributes.fetch_value(name, &block)
       end
 
       # This method exists to avoid the expensive primary_key check internally, without

activerecord/lib/active_record/attribute_methods/write.rb

@@ -31,14 +31,13 @@ module ActiveRecord
         name = self.class.attribute_aliases[name] || name
 
         name = @primary_key if name == "id" && @primary_key
-        _write_attribute(name, value)
+        @attributes.write_from_user(name, value)
       end
 
       # This method exists to avoid the expensive primary_key check internally, without
       # breaking compatibility with the write_attribute API
       def _write_attribute(attr_name, value) # :nodoc:
         @attributes.write_from_user(attr_name, value)
-        value
       end
 
       alias :attribute= :_write_attribute
@@ -47,7 +46,6 @@ module ActiveRecord
       private
         def write_attribute_without_type_cast(attr_name, value)
           @attributes.write_cast_value(attr_name, value)
-          value
         end
     end
   end