TagSetPresenter: refactor tag string for post edit form.

Move PostPresenter#categorized_tag_groups to TagSetPresenter#split_tag_list_text.

This allows split_tag_list_text to reuse the same set of tags already
fetched by the tag set presenter for the sidebar.

This avoids a memcache call to get the tag categories when rendering the
tag string for the post edit form.

app/presenters/post_presenter.rb

@@ -1,6 +1,6 @@
 class PostPresenter < Presenter
   attr_reader :pool, :next_post_in_pool
-  delegate :tag_list_html, :split_tag_list_html, :inline_tag_list_html, to: :tag_set_presenter
+  delegate :tag_list_html, :split_tag_list_html, :split_tag_list_text, :inline_tag_list_html, to: :tag_set_presenter
 
   def self.preview(post, options = {})
     if post.nil?
@@ -151,22 +151,6 @@ class PostPresenter < Presenter
     "#{humanized_essential_tag_string} - #{@post.md5}.#{@post.file_ext}"
   end
 
-  def categorized_tag_groups
-    string = []
-
-    TagCategory.categorized_list.each do |category|
-      if @post.typed_tags(category).any?
-        string << @post.typed_tags(category).join(" ")
-      end
-    end
-    
-    string
-  end
-
-  def categorized_tag_string
-    categorized_tag_groups.join(" \n")
-  end
-
   def safe_mode_message(template)
     html = ["This image is unavailable on safe mode (#{Danbooru.config.app_name}). Go to "]
     html << template.link_to("Danbooru", "https://danbooru.donmai.us") # XXX don't hardcode.