Add usage overview graphql query

What does this MR do and why?

Adds a new graphql query for the usage overview counts. This MR:

• Adds the new query that will be used in VSD - [FE] adding "Usage overview" panel" (!136536 - merged)
• Adds an additional nYearsBefore method for finding dates a specified number of years in the past
• Adds related tests

Screenshots or screen recordings

No visual changes

How to set up and validate locally

$ yarn jest --watch data_sources/usage_overview_spec date_calculation

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.

Related to #386842 (closed)