Adds namespace fixtures and specs for usage_quotas/utils

What does this MR do and why?

Fixes the #347011 :

1. It adds a fixture generator for namespace_storage.query.graphql, which is then used in .js tests

2. Adds specs for usage_quotas/utils.js > getStorageTypesFromProjectStatistics

Screenshots or screen recordings

n/a

How to set up and validate locally

Generate fixtures via rspec ee/spec/frontend/fixtures/namespace.rb

Run JS specs for usage quotas via npx jest --watch ee/spec/frontend/usage_quotas/storage/

MR acceptance checklist

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