Add product analytics usage visualization to show the total usage for the group

Proposal

As part of Product Analytics Usage Quota MVC Implementatio... (#419407 - closed) we need to create a new visualization to show to the groups total usage. The visualization should show the previous billing periods usage and the usage so far for the current billing period.

This could be two progress bars like:

This would be dependent on the final designs.

Furthermore, we need to also add documentation to note the new usage quota feature.

Designs

header	header
loading
error
empty state	TODO separately

Implementation plan – frontend

Note: builds on previous usage table or usage visualization issue

• create new total usage visualization component
  • duplicates query and loading/error states from projects-usage component (fetches current + previous months project usage data)
  • note: duplicated query will later be swapped out when we fetch a years worth of data instead of two months, which is why I'm not sharing / reusing stuff from the existing component
  • sum the data so we have the total counts for all projects for current / previous month
  • display data using an area chart
  • Add note at top of section Product analytics usage is calculated based on number of events received. Learn more.
• check spacing/padding/header levels etc for consistency with Pipelines usage quota page
• tests
• add documentation for this new usage quota section. Link to it from section header with a Learn More link.