FE: Usage Quotas page standardization - Error/Loading state

The goal is to have a proper loading/error state for the Usage Quotas Page Statistics and StatisticsSeats cards.

The following discussion from !82399 (merged) should be addressed:

• @dzubova started a discussion: (+2 comments)

  question: How should the page look when the API is error and/or when the page is loading?

  Should we show the two tiles at all? If yes, should we show 0/0 everywhere?

  @mnearents I think you could help us here with UX insights 😄

  

Summary

• Loading: We should add Skeleton Loaders wrapper for both Statistics and StatisticsSeats
• Error: On API error we should persists the skeleton loaders and show an alert banner at the top of the page with the following text: Something went wrong while loading Usage details

Old design suggestion

question: should we still show the alert above? @mnearents

Description updated after confirming of correct behaviour.

Availability & Testing

Regarding this change a view/jest or a feature spec would suffice to check that when the API error is returned a correct error message is shown and when Loading is in progress the loader is visible.