Add allocations to template renderer subscription

This PR adds the allocations to the instrumentation for template and
partial rendering.

Before:

```
  Rendering posts/new.html.erb within layouts/application
  Rendered posts/_form.html.erb (9.7ms)
  Rendered posts/new.html.erb within layouts/application (10.9ms)
Completed 200 OK in 902ms (Views: 890.8ms | ActiveRecord: 0.8ms)
```

After:

```
  Rendering posts/new.html.erb within layouts/application
  Rendered posts/_form.html.erb (Duration: 7.1ms | Allocations: 6004)
  Rendered posts/new.html.erb within layouts/application (Duration: 8.3ms | Allocations: 6654)
Completed 200 OK in 858ms (Views: 848.4ms | ActiveRecord: 0.4ms | Allocations: 1539564)
```

1 files changed, 5 insertions, 2 deletions

diff --git a/actionpack/lib/action_controller/log_subscriber.rb b/actionpack/lib/action_controller/log_subscriber.rb
index 6de1fb2c19..afbd38e7fe 100644
--- a/actionpack/lib/action_controller/log_subscriber.rb
+++ b/actionpack/lib/action_controller/log_subscriber.rb
@@ -18,14 +18,17 @@ module ActionController
 
     def process_action(event)
       info do
-        payload   = event.payload
+        payload = event.payload
         additions = ActionController::Base.log_process_action(payload)
-
         status = payload[:status]
+
         if status.nil? && payload[:exception].present?
           exception_class_name = payload[:exception].first
           status = ActionDispatch::ExceptionWrapper.status_code_for_exception(exception_class_name)
         end
+
+        additions << "Allocations: #{event.allocations}"
+
         message = +"Completed #{status} #{Rack::Utils::HTTP_STATUS_CODES[status]} in #{event.duration.round}ms"
         message << " (#{additions.join(" | ")})" unless additions.empty?
         message << "\n\n" if defined?(Rails.env) && Rails.env.development?