Private process action

[etiennebarrie]

Summary

AbstractController::Base defines process_action as private, but modules included after redefine it as a public method.

I also fixed the indentation in actionpack/lib/action_controller/metal/instrumentation.rb, I kept it separate for easier review but I can squash it.

Other Information

Doing this removes process_action from the docs (there's still ActionController::LogSubscriber#process_action).

Maybe we should make it visible to the documentation in AbstractController::Base, given the comment and the fact that it's then overridden by things outside actionpack like ActiveRecord::Railties::ControllerRuntime:

rails/actionpack/lib/abstract_controller/base.rb

Lines 221 to 223 in 75ac626

	# Call the action. Override this in a subclass to modify the
	# behavior around processing an action. This, and not #process,
	# is the intended way to override action dispatching.

cc @rafaelfranca @byroot