Add an every metric definition CE test

What does this MR do and why?

Related to #342711 (closed)

We want to make sure that CE Service Ping includes only the keys for metrics that are defined in CE namespace. So far, we only had a similar test running on EE, so it wasn't able to verify the CE keys accuracy.

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Before	After

How to set up and validate locally

1. Add a change that breaks the CE Usage Ping to metrics definition parity: for example, move a CE metric definition into the EE namespace or add a new metric inside usage_data.rb
2. Try running the new test with the FOSS_ONLY=1 env variable set. It should fail now.

I have already tested these changes here: !122491 (closed), the failing job

MR acceptance checklist

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