Add test for graphql query complexity

What does this MR do and why?

Add an RSpec test which verifies that none of the GraphQL queries in the app are exceeding the complexity limit. In #580576 (closed), we had a bug where the vulnerability report query started hitting the complexity limit in production which broke functionality. This test should prevent similar issues from happening for new queries.

References

Relates to: #581051 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

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