Add metrics for 'Open workspace' button

What does this MR do and why?

We plan to track 'Open workspace' click event, and make also make metrics for it.

References

• Issue - Add metric for clicking `Open workspace` button (#543081 - closed)
• Doc reference - https://docs.gitlab.com/development/internal_analytics/internal_event_instrumentation/quick_start/#frontend-tracking

Screenshots or screen recordings

How to set up and validate locally

• Follow steps for local workspace setup, https://gitlab.com/gitlab-org/workspaces/gitlab-workspaces-docs/-/blob/main/doc/local-development-environment-setup.md?ref_type=heads
• Follow steps for local snowplow micro setup, https://docs.gitlab.com/development/internal_analytics/internal_event_instrumentation/local_setup_and_debugging/#snowplow-micro
• Go to workspace creation page http://gdk.test:3000/-/remote_development/workspaces/new, and create one workspace. Wait it for it in the Running state
• Click on the button Open workspace button, and see the event is tracked as expected

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.