FEATURE: Promote bookmarks with reminders to core functionality (#9369)

The main thrust of this PR is to take all the conditional checks based on the `enable_bookmarks_with_reminders` away and only keep the code from the `true` path, making bookmarks with reminders the core bookmarks feature. There is also a migration to create `Bookmark` records out of `PostAction` bookmarks for a site.

### Summary

* Remove logic based on whether enable_bookmarks_with_reminders is true. This site setting is now obsolete, the old bookmark functionality is being removed. Retain the setting and set the value to `true` in a migration.
* Use the code from the rake task to create a database migration that creates bookmarks from post actions.
* Change the bookmark report to read from the new table.
* Get rid of old endpoints for bookmarks
* Link to the new bookmarks list from the user summary page

test/javascripts/acceptance/topic-test.js

@@ -397,10 +397,7 @@ QUnit.test(
 );
 
 acceptance("Topic + Post Bookmarks with Reminders", {
-  loggedIn: true,
-  settings: {
-    enable_bookmarks_with_reminders: true
-  }
+  loggedIn: true
 });
 
 QUnit.test("Bookmarks Modal", async assert => {