Add metric for clicking Open workspace button

MR: Add metrics for 'Open workspace' button (!192315 - merged)

Description

We plan to add one metric for tracking user activity for clicking Open workspace button.

The event definition remains the same as normal, and we use the event tracking on the frontend instead. See doc for more details, https://docs.gitlab.com/development/internal_analytics/internal_event_instrumentation/quick_start/#frontend-tracking

On Service Ping metric, we plan to make one metric for tracking all data, for period 7d, 28d and all time.

The workspace button is defined here, ee/app/assets/javascripts/workspaces/common/components/open_workspace_button.vue

Acceptance criteria

• Define the internal event for tracking button click activity
• Trigger the event when the button is clicked
• Define Service Ping metric for above event for 7d, 28d and all time timeframe.

Implementation plan

NA