Tag image after booting and include destination

If you are deploying more than one destination to a host, the latest
tags will conflict, so we'll append the destination to the tag.

The latest tag is used when booting the app or exec-ing a new container.

If a deploy doesn't complete on a host for all roles then we should
probably not be using it, so move the tagging to the end of the boot
process.

lib/kamal/commands/app/images.rb

@@ -7,7 +7,7 @@ module Kamal::Commands::App::Images
     docker :image, :prune, "--all", "--force", *filter_args
   end
 
-  def tag_current_image_as_latest
+  def tag_latest_image
     docker :tag, config.absolute_image, config.latest_image
   end
 end