Use Rails 5.2 Redis caching store

In GitLab v12.2.0, we enabled the Rails Redis caching store in
production
(https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/30966). However,
we had to to revert this in 6bda359b
because Rack Attack v4.4.1 wasn't fully compatible with this store and
caused fatal errors when rate limits were enabled
(https://github.com/kickstarter/rack-attack/issues/281).

Now that we have upgraded to Rack Attack v6.2.0, which pulls in
https://github.com/kickstarter/rack-attack/pull/340, this caching store
is now supported. This is validated by the GitLab QA tests introduced
in https://gitlab.com/gitlab-org/gitlab-foss/merge_requests/32177.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/64794

changelogs/unreleased/sh-use-rails-redis-store.yml

+---
+title: Use Rails 5.2 Redis caching store
+merge_request: 19202
+author:
+type: other

config/application.rb

@@ -247,7 +247,10 @@ module Gitlab
     end
 
     # Use caching across all environments
+    # Full list of options:
+    # https://api.rubyonrails.org/classes/ActiveSupport/Cache/RedisCacheStore.html#method-c-new
     caching_config_hash = Gitlab::Redis::Cache.params
+    caching_config_hash[:compress] = false
     caching_config_hash[:namespace] = Gitlab::Redis::Cache::CACHE_NAMESPACE
     caching_config_hash[:expires_in] = 2.weeks # Cache should not grow forever
     if Sidekiq.server? # threaded context
@@ -255,7 +258,7 @@ module Gitlab
       caching_config_hash[:pool_timeout] = 1
     end
 
-    config.cache_store = :redis_store, caching_config_hash
+    config.cache_store = :redis_cache_store, caching_config_hash
 
     config.active_job.queue_adapter = :sidekiq