Add metrics for distinct active workspace users

What does this MR do and why?

Introduce workspace active user metric by utilising our existing events.

• Event for clicking Open workspace button defined here, which could fit into opens a workspace
• Event for tracking workspace creation event defined here, which could fit into creates a workspace
• Event for tracking active workspace defined here, which could fit into restarts a suspended workspace

We only count distinct event by user.id

References

Issue - Add metrics for distinct active workspace users (#537568 - closed)

Screenshots or screen recordings

Tried with below approach on the new metric.

• Create one workspace first; click Open workspace a few times with the same user; and see only one counter increase on the unique user_id metric introduced.
• Then triggered event with different user signed in; and see the counter increased by one again

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, and see event tracked with started label when workspace is running
• Click on button Open workspace
• Verify only 1 counter increase for the same user
• Sign in with a different user, and repeat above steps
• Verify another 1 counter increase for this new user

MR acceptance checklist

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