Adds instrumentation to interpolation

What does this MR do and why?

Adds instrumentation to interpolation: #396722 (closed)

How to set up and validate locally

1. Observe that the Service Ping payload includes ci_interpolation_users_monthly and ci_interpolation_users_weekly subkeys.

Run the following commands in the console:

service_ping_payload = Gitlab::Usage::ServicePingReport.for(output: :non_sql_metrics_values)
service_ping_payload['redis_hll_counters']['pipeline_authoring']

2. Run the following command and note the outputted value (it should be 0 if you haven't run Step 4 yet).

::Gitlab::UsageDataCounters::HLLRedisCounter.unique_events(event_names: 'ci_interpolation_users', start_date: Date.today, end_date: Date.today + 7.days, context: '')

3. Go to your Project's CI/CD Editor and update the contents with:

#.gitlab-ci.yml
include:
  - local: template.yml
    inputs:
      stage: deploy
      job_prefix: "my-app-"

#template.yml
spec:
  inputs:
    stage:   
      default: test
    job_prefix:
      default: "" 
---    
"$[[ inputs.job_prefix]]deploy":
  stage: $[[ inputs.stage ]]
  script: echo "deploy $[[ inputs.stage ]]"

4. Commit the changes and wait for the pipeline to complete running. Now observe the counter value again. It should have incremented by 1.

::Gitlab::UsageDataCounters::HLLRedisCounter.unique_events(event_names: 'ci_interpolation_users', start_date: Date.today, end_date: Date.today + 7.days, context: '')

5. If you'd like to see the Service Ping payload counters incremented, then you can track a mocked event set to a week ago and then check the Service Ping payload output.

::Gitlab::UsageDataCounters::HLLRedisCounter.track_event('ci_interpolation_users', values: 1, time: Date.today - 7.days)
service_ping_payload = Gitlab::Usage::ServicePingReport.for(output: :non_sql_metrics_values)
service_ping_payload['redis_hll_counters']['pipeline_authoring']

NOTE: Huge shoutout and thank you to @lma-git for providing these steps for testing the instrumentation. 🙇

Once this is merged

you can see the query in: https://metrics.gitlab.com/?q=interpolation, and then use that to add a widget to Sisense.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.