Add codeowners to usage data

Problem

Usage of codeowners feature is not currently instrumented

Proposal

Add codeowners to usage data, we are aiming to answer the following questions:

1. How many repositories contain a codeowners file?

• What is the percentage repositories using codeowners?
• What is the percentage of customers using codeowners (namespace for GitLab.com, instance for self-managed)

2. Out of the total number of codeowners files, how many of those files are making use of the sectional codeowners feature? (not sure if this one is doable)

Further info