VSA - Refactor metrics component

Follow-up from !59732 (comment 564453940) and !59732 (comment 564497870)

Let's refactor the metrics component address the following two issues:

• Combine the two instances of the TimeMetricsCard component into a single component in https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/assets/javascripts/analytics/cycle_analytics/components/metrics.vue#L28
• On mobile alignment, we want to show three metrics on top and two metrics below. (Currently we show 2 on top and 3 below).