Fix performance of home feed regeneration (#12084)

Fetching statuses from all followed accounts at once takes too long
within Postgres. Fetching them one by one and merging in Ruby
could be a lot less resource-intensive

Because the query for dynamically fetching the home timeline is so
heavy, we can no longer offer it when the home timeline is missing

app/models/home_feed.rb

@@ -7,19 +7,7 @@ class HomeFeed < Feed
     @account = account
   end
 
-  def get(limit, max_id = nil, since_id = nil, min_id = nil)
-    if redis.exists("account:#{@account.id}:regeneration")
-      from_database(limit, max_id, since_id, min_id)
-    else
-      super
-    end
-  end
-
-  private
-
-  def from_database(limit, max_id, since_id, min_id)
-    Status.as_home_timeline(@account)
-          .paginate_by_id(limit, max_id: max_id, since_id: since_id, min_id: min_id)
-          .reject { |status| FeedManager.instance.filter?(:home, status, @account.id) }
+  def regenerating?
+    redis.exists("account:#{@id}:regeneration")
   end
 end