Add time frames handling to TotalCountMetric

What does this MR do and why?

Related to #411264 (closed)

We want to make it possible to create Redis metrics that are contained inside 7d/28d time frames.

To handle that, we will be saving the periodic redis data under weekly redis keys. This is based on a PoC: !120845 (diffs)

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Before	After

How to set up and validate locally

1. Back on master branch, visit the analytics dashboard page:
   • Make sure that Service ping is enabled: ::ServicePing::ServicePingSettings.enabled? should return true in the console. If it doesn't - check how to enable Service ping here
   • Enter a project and go to Analyze -> Analytics Dashboard. This may require enabling a feature flag, more details here
   • Enter a dashboard from the list
2. Make sure that you triggered some events, by running redis_counter_key = Gitlab::Usage::Metrics::Instrumentations::TotalCountMetric.redis_key('user_visited_dashboard', Date.today); Gitlab::Redis::SharedState.with { |redis| redis.get(redis_counter_key) } in the console: it should return a number bigger than 0.
3. Check out this MR's branch
4. Refresh the dashboard analytics page. Verify that the old redis counter is still working, by making sure that Gitlab::Redis::SharedState.with { |redis| redis.get(redis_counter_key) } still increases after reloading the website.
5. Make it possible to time travel, by running require 'active_support/testing/time_helpers' and then include ActiveSupport::Testing::TimeHelpers
6. To also verify monthly statistics, trigger additional events 2 and 5 weeks ago: [-2.weeks, -5.weeks]. each { |period| travel(period) { Gitlab::InternalEvents.track_event('user_visited_dashboard', user: User.first) } }. This should make it so that the monthly redis count is set to 1 more than the weekly count (as only the event happening 2 weeks ago should make the cut for a monthly range).
7. Generate next week's service ping: sp = travel(1.week) { Gitlab::Usage::ServicePingReport.for(output: :all_metrics_values) }
8. Check the values for periodic redis metrics: sp['counts'].values_at('analytics_dashboard_visits_monthly', 'analytics_dashboard_visits_weekly'). The values should correspond to monthly/weekly/total times the analytics dashboard website has been visited. Monthly count should be higher than the weekly count by 1 [as it has been simulated in point 6].

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