Convert performance_bar_stats to an ops feature flag

<!-- Title suggestion: [Feature flag] Enable description of feature --> ## What Remove the `:performance_bar_stats` feature flag introduced in https://gitlab.com/gitlab-org/gitlab/-/merge_requests/48149 ## Owners - Team: Plan - Most appropriate slack channel to reach out to: `#g_plan` - Best individual to reach out to: jprovaznik ## Expectations ### What are we expecting to happen? Data are logged in performance_bar_log_json.log ### What might happen if this goes wrong? Increased load due to async job which proceses peek stats (in case there would be extreme amount of these stats) - which is low chance - we delete peek redis data after 30 minutes. ### What can we monitor to detect problems with this? Sidekiq job (app/workers/gitlab_performance_bar_stats_worker.rb), size of performance_bar_log_json.log file ## Beta groups/projects If applicable, any groups/projects that are happy to have this feature turned on early. Some organizations may wish to test big changes they are interested in with a small subset of users ahead of time for example. This feature is enabled/disabled globally. ## Roll Out Steps - [x] Enable on staging (`/chatops run feature set feature_name true --staging`) - [x] Test on staging - [x] Ensure that documentation has been updated - [x] Enable on GitLab.com for individual groups/projects listed above and verify behaviour (`/chatops run feature set --project=gitlab-org/gitlab feature_name true`) - [x] Coordinate a time to enable the flag with the SRE oncall and release managers - In `#production` by pinging `@sre-oncall` - In `#g_delivery` by pinging `@release-managers` - [ ] ~Announce on the issue an estimated time this will be enabled on GitLab.com~ - [x] Enable on GitLab.com by running chatops command in `#production` (`/chatops run feature set feature_name true`) - [x] Cross post chatops Slack command to `#support_gitlab-com` ([more guidance when this is necessary in the dev docs](https://docs.gitlab.com/ee/development/feature_flags/controls.html#where-to-run-commands)) and in your team channel - [x] Announce on the issue that the flag has been enabled - [ ] ~Remove feature flag and add changelog entry~ - [ ] ~After the flag removal is deployed, [clean up the feature flag](https://docs.gitlab.com/ee/development/feature_flags/controls.html#cleaning-up) by running chatops command in `#production` channel~ ## Rollback Steps - [ ] This feature can be disabled by running the following Chatops command: ``` /chatops run feature set --project=gitlab-org/gitlab performance_bar_stats false ```

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