Track clicked templates for pipeline empty state experiment

What does this MR do?

Issue: gitlab-org/growth/team-tasks#310 (closed)

This is an experiment to list CI templates when there is no CI set up for a project yet. In this MR we add tracking of the templates that get used by tracking the click on them.

Description	MR
List templates in empty pipeline state	!57286 (merged)
Add "Hello World" template to empty pipeline experiment	!58649 (merged)
Track usage of templates	👈 you are here

Screenshots (strongly suggested)

Page	Snowplow Event

How to test locally

Note: There might be a bit of a caching issue with feature flags & experiments that other reviewers already experienced that requires restarting the gdk if you want to check out both versions.

• checkout branch
• yarn
• echo 'Feature.enable(:pipeline_empty_state_templates)' | bin/rails c
• Create or go to a project without a .gitlab-ci.yml
• Disabled "Default to Auto DevOps pipeline" in the CI/CD settings of your project (http://localhost:3000/<group_name>/<project_name>/-/settings/ci_cd
• Go to CI/CD -> Pipelines (http://localhost:3000/<group_name>/<project_name>/-/pipelines

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because it's behind the experiment feature flag.
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team