Improve Rails' Shape friendliness (second pass)

Followup: #47023

```
Shape Edges Report
-----------------------------------
snip...
       238  @errors
snip...
       219  @options
snip...
       129  @_request
       128  @type
       125  @virtual_path
       124  @_assigns
       123  @_config
       123  @_controller
       123  @output_buffer
       123  @view_flow
       122  @_default_form_builder
snip...
        89  @_already_called
        75  @validation_context
snip...
        65  @_new_record_before_last_commit
snip...
        58  @_url_options
snip...
```

actionpack/lib/action_controller/metal.rb

@@ -137,6 +137,17 @@ def self.action_encoding_template(action) # :nodoc:
       false
     end
 
+    class << self
+      private
+        def inherited(subclass)
+          super
+          subclass.middleware_stack = middleware_stack.dup
+          subclass.class_eval do
+            @controller_name = nil
+          end
+        end
+    end
+
     # Delegates to the class's ::controller_name.
     def controller_name
       self.class.controller_name
@@ -166,7 +177,9 @@ def controller_name
     def initialize
       @_request = nil
       @_response = nil
+      @_response_body = nil
       @_routes = nil
+      @_params = nil
       super
     end
 
@@ -240,11 +253,6 @@ def reset_session
 
     class_attribute :middleware_stack, default: ActionController::MiddlewareStack.new
 
-    def self.inherited(base) # :nodoc:
-      base.middleware_stack = middleware_stack.dup
-      super
-    end
-
     class << self
       # Pushes the given Rack middleware and its arguments to the bottom of the
       # middleware stack.

actionview/lib/action_view/base.rb

@@ -205,7 +205,8 @@ def changed?(other) # :nodoc:
     delegate :formats, :formats=, :locale, :locale=, :view_paths, :view_paths=, to: :lookup_context
 
     def assign(new_assigns) # :nodoc:
-      @_assigns = new_assigns.each { |key, value| instance_variable_set("@#{key}", value) }
+      @_assigns = new_assigns
+      new_assigns.each { |key, value| instance_variable_set("@#{key}", value) }
     end
 
     # :stopdoc:
@@ -232,9 +233,13 @@ def initialize(lookup_context, assigns, controller) # :nodoc:
       @view_renderer = ActionView::Renderer.new @lookup_context
       @current_template = nil
 
-      assign(assigns)
       assign_controller(controller)
       _prepare_context
+
+      super()
+
+      # Assigns must be called last to minimize the number of shapes
+      assign(assigns)
     end
 
     def _run(method, template, locals, buffer, add_to_stack: true, has_strict_locals: false, &block)

actionview/lib/action_view/helpers/controller_helper.rb

@@ -20,6 +20,10 @@ def assign_controller(controller)
           @_request = controller.request if controller.respond_to?(:request)
           @_config  = controller.config.inheritable_copy if controller.respond_to?(:config)
           @_default_form_builder = controller.default_form_builder if controller.respond_to?(:default_form_builder)
+        else
+          @_request ||= nil
+          @_config ||= nil
+          @_default_form_builder ||= nil
         end
       end
 

actionview/lib/action_view/test_case.rb

@@ -225,6 +225,10 @@ def view
         :@_result,
         :@_routes,
         :@controller,
+        :@_controller,
+        :@_request,
+        :@_config,
+        :@_default_form_builder,
         :@_layouts,
         :@_files,
         :@_rendered_views,
@@ -243,7 +247,7 @@ def view
         :@view_context_class,
         :@view_flow,
         :@_subscribers,
-        :@html_document
+        :@html_document,
       ]
 
       def _user_defined_ivars

activemodel/lib/active_model/validations.rb

@@ -433,6 +433,7 @@ def validate!(context = nil)
   private
     def init_internals
       super
+      @errors = nil
       @validation_context = nil
     end
 

activerecord/lib/active_record/attribute_methods/dirty.rb

@@ -187,6 +187,8 @@ def init_internals
           super
           @mutations_before_last_save = nil
           @mutations_from_database = nil
+          @_touch_attr_names = nil
+          @_skip_dirty_tracking = nil
         end
 
         def _touch_row(attribute_names, time)

activerecord/lib/active_record/autosave_association.rb

@@ -154,13 +154,6 @@ def self.valid_options
 
     module ClassMethods # :nodoc:
       private
-        def inherited(base)
-          super
-          base.class_eval do
-            @_already_called = nil
-          end
-        end
-
         def define_non_cyclic_method(name, &block)
           return if method_defined?(name, false)
 
@@ -280,6 +273,11 @@ def changed_for_autosave?
     end
 
     private
+      def init_internals
+        super
+        @_already_called = nil
+      end
+
       # Returns the record for an association collection that should be validated
       # or saved. If +autosave+ is +false+ only new records will be returned,
       # unless the parent is/was a new record itself.

activerecord/lib/active_record/persistence.rb

@@ -1123,6 +1123,7 @@ def touch(*names, time: nil)
     def init_internals
       super
       @_trigger_destroy_callback = @_trigger_update_callback = nil
+      @previously_new_record = false
     end
 
     def strict_loaded_associations

activerecord/lib/active_record/touch_later.rb

@@ -46,6 +46,11 @@ def touch(*names, time: nil) # :nodoc:
     end
 
     private
+      def init_internals
+        super
+        @_defer_touch_attrs = nil
+      end
+
       def surreptitiously_touch(attr_names)
         attr_names.each do |attr_name|
           _write_attribute(attr_name, @_touch_time)

activerecord/lib/active_record/transactions.rb

@@ -370,7 +370,9 @@ def trigger_transactional_callbacks? # :nodoc:
 
       def init_internals
         super
+        @_start_transaction_state = nil
         @_committed_already_called = nil
+        @_new_record_before_last_commit = nil
       end
 
       # Save the new record state and id of a record so it can be restored later if a transaction fails.

activesupport/lib/active_support/encrypted_configuration.rb

@@ -46,6 +46,8 @@ def message
     def initialize(config_path:, key_path:, env_key:, raise_if_missing_key:)
       super content_path: config_path, key_path: key_path,
         env_key: env_key, raise_if_missing_key: raise_if_missing_key
+      @config = nil
+      @options = nil
     end
 
     # Reads the file and returns the decrypted content. See EncryptedFile#read.

activesupport/lib/active_support/number_helper/number_converter.rb

@@ -121,7 +121,8 @@ def self.convert(number, options)
 
       def initialize(number, options)
         @number = number
-        @opts   = options.symbolize_keys
+        @opts = options.symbolize_keys
+        @options = nil
       end
 
       def execute