posts/index: fix rating:s being included in page title in safe mode.

Fixes bug described in d3e4ac7c17 (commitcomment-39049351)

When dealing with searches, there are several variables we have to keep
in mind:

* Whether tag aliases should be applied.
* Whether search terms should be sorted.
* Whether the rating:s and -status:deleted metatags should be added by
  safe mode and the hide deleted posts setting.

Which of these things we need to do depends on the context:

* We want to apply aliases when actually doing the search, calculating
  the count, looking up the wiki excerpt, recording missed/popular
  searches in Reportbooru, and calculating related tags for the sidebar,
  but not when displaying the raw search as typed by the user (for
  example, in the page title or in the tag search box).
* We want to sort the search when calculating cache keys for fast_count
  or related tags, and when recording missed/popular searches, but not
  in the page title or when displaying the raw search.
* We want to add rating:s and -status:deleted when performing the
  search, calculating the count, or recording missed/popular searches,
  but not when calculating related tags for the sidebar, or when
  displaying the page title or raw search.

Here we introduce normalized_query and try to use it in contexts where
query normalization is necessary. When to use the normalized query
versus the raw unnormalized query is still subtle and prone to error.

app/logical/post_sets/post.rb

@@ -4,6 +4,7 @@ module PostSets
     MAX_SIDEBAR_TAGS = 25
 
     attr_reader :page, :random, :post_count, :format, :tag_string, :query
+    delegate :normalized_query, to: :query
 
     def initialize(tags, page = 1, per_page = nil, random: false, format: "html")
       @query = PostQueryBuilder.new(tags, CurrentUser.user, safe_mode: CurrentUser.safe_mode?, hide_deleted_posts: CurrentUser.hide_deleted_posts?)
@@ -29,8 +30,8 @@ module PostSets
     end
 
     def tag
-      return nil unless query.has_single_tag?
-      @tag ||= Tag.find_by(name: query.tags.first.name)
+      return nil unless normalized_query.has_single_tag?
+      @tag ||= Tag.find_by(name: normalized_query.tags.first.name)
     end
 
     def artist
@@ -40,7 +41,7 @@ module PostSets
     end
 
     def pool
-      pool_names = query.select_metatags(:pool, :ordpool).map(&:value)
+      pool_names = normalized_query.select_metatags(:pool, :ordpool).map(&:value)
       name = pool_names.first
       return nil unless pool_names.size == 1
 
@@ -48,7 +49,7 @@ module PostSets
     end
 
     def favgroup
-      favgroup_names = query.select_metatags(:favgroup, :ordfavgroup).map(&:value)
+      favgroup_names = normalized_query.select_metatags(:favgroup, :ordfavgroup).map(&:value)
       name = favgroup_names.first
       return nil unless favgroup_names.size == 1
 
@@ -88,7 +89,7 @@ module PostSets
         # no need to get counts for formats that don't use a paginator
         nil
       else
-        query.fast_count
+        normalized_query.fast_count
       end
     end
 
@@ -105,7 +106,7 @@ module PostSets
         if is_random?
           temp = get_random_posts
         else
-          temp = query.build.paginate(page, count: post_count, search_count: !post_count.nil?, limit: per_page)
+          temp = normalized_query.build.paginate(page, count: post_count, search_count: !post_count.nil?, limit: per_page)
         end
       end
     end
@@ -176,7 +177,7 @@ module PostSets
       end
 
       def similar_tags
-        RelatedTagCalculator.cached_similar_tags_for_search(query, MAX_SIDEBAR_TAGS)
+        RelatedTagCalculator.cached_similar_tags_for_search(normalized_query(implicit: false), MAX_SIDEBAR_TAGS)
       end
 
       def frequent_tags