DEV: Topic tracking state improvements (#12958)

Original PR which had to be reverted **https://github.com/discourse/discourse/pull/12555**. See the description there for what this PR is achieving, plus below.

The issue with the original PR is addressed in 92ef54f402

If you went to the `x unread` link for a tag Chrome would freeze up and possibly crash, or eventually unfreeze after nearly 10 mins. Other routes for unread/new were similarly slow. From profiling the issue was the `sync` function of `topic-tracking-state.js`, which calls down to `isNew` which in turn calls `moment`, a change I had made in the PR above. The time it takes locally with ~1400 topics in the tracking state is 2.3 seconds.

To solve this issue, I have moved these calculations for "created in new period" and "unread not too old" into the tracking state serializer.

When I was looking at the profiler I also noticed this issue which was just compounding the problem. Every time we modify topic tracking state we recalculate the sidebar tracking/everything/tag counts. However this calls `forEachTracked` and `countTags` which can be quite expensive as they go through the whole tracking state (and were also calling the removed moment functions).

I added some logs and this was being called 30 times when navigating to a new /unread route because  `sync` is being called from `build-topic-route` (one for each topic loaded due to pagination). So I just added a debounce here and it makes things even faster.

Finally, I changed topic tracking state to use a Map so our counts of the state keys is faster (Maps have .size whereas objects you have to do Object.keys(obj) which is O(n).)

app/controllers/topics_controller.rb

@@ -919,7 +919,7 @@ class TopicsController < ApplicationController
       topic_ids = params[:topic_ids].map { |t| t.to_i }
     elsif params[:filter] == 'unread'
       tq = TopicQuery.new(current_user)
-      topics = TopicQuery.unread_filter(tq.joined_topic_user, current_user.id, staff: guardian.is_staff?).listable_topics
+      topics = TopicQuery.unread_filter(tq.joined_topic_user, staff: guardian.is_staff?).listable_topics
       topics = TopicQuery.tracked_filter(topics, current_user.id) if params[:tracked].to_s == "true"
 
       if params[:category_id]