FEATURE: support search click through tracking for user, category and tags

https://meta.discourse.org/t/search-logs-page/73281/11?u=techapj

This commit adds following features:

- support for tracking click through to user, tag and category
- new filter for search type (header, full page)

This commit also removes "most viewed topic" field from search logs page because we are now tracking multiple click through entities, so topic is not a special entity anymore. This also improves query perf. The query now takes `20.5ms` to runs, as opposed to `655.9ms` previously.

app/assets/javascripts/admin/templates/logs/search-logs.hbs

@@ -1,5 +1,6 @@
 <p>
   {{period-chooser period=period}}
+  {{combo-box content=searchTypeOptions value=searchType class='search-logs-filter'}}
 </p>
 <br>
 
@@ -11,7 +12,6 @@
         <div class="col heading term">{{i18n 'admin.logs.search_logs.term'}}</div>
         <div class="col heading">{{i18n 'admin.logs.search_logs.searches'}}</div>
         <div class="col heading">{{i18n 'admin.logs.search_logs.click_through'}}</div>
-        <div class="col heading topic">{{i18n 'admin.logs.search_logs.most_viewed_topic'}}</div>
         <div class="col heading" title="{{i18n 'admin.logs.search_logs.unique_title'}}">{{i18n 'admin.logs.search_logs.unique'}}</div>
       </div>
 
@@ -20,11 +20,6 @@
           <div class="col term">{{item.term}}</div>
           <div class="col">{{item.searches}}</div>
           <div class="col">{{item.click_through}}</div>
-          <div class="col topic">
-            {{#if item.clicked_topic_id}}
-              <a href='{{unbound item.topic_url}}'>{{item.topic_title}}</a>
-            {{/if}}
-          </div>
           <div class="col">{{item.unique}}</div>
         </div>
       {{/each}}