recording_ce_finish_data should be done last time in usage_ping_generation

The following discussion from !32315 (merged) should be addressed:

Find a way to ensure merge(recording_ce_finish_data) is done last time in usage_ping_generation

Feedback from @splattael

> Could we have this moved one step above? we want to have the tine the usage ping takes to generated and `recording_ce_finish_data` is going to take a timestamp at the end

Something like:

          .merge(recording_ce_finish_data) # Needs to come last to take the timestamp at the end

Alternatively, we could move it out of uncached_data and add it in def data:

      def data(force_refresh: false)
        Rails.cache.fetch('usage_data', force: force_refresh, expires_in: 2.weeks) do
          uncached_data.merge(recording_ce_finish_data)
        end
      end

...but ☝ won't play nice with the EE extension (https://gitlab.com/gitlab-org/gitlab/-/blob/26f1bd728953e52a0bfa264616a03570a67aba40/ee/lib/ee/gitlab/usage_data.rb#L41) I suppose 😞

cc: @splattael @mkaeppler

Edited by Alina Mihaila