Replace hardcoded mock job data with fixtures (2)

What does this MR do and why?

Replace hardcoded mock job data with a fixtures.

This fixtures are generated by the same queries that are used in the frontend, allowing them to stay in sync with the frontend changes.

Note I added pipeline:skip-undercoverage while #366653 (closed) is resolved.

Why?

I decided to work on this as part of the devopsverify Hackathon week so it has no issue attached, it's just something I have been meaning to do!

Screenshots or screen recordings

NA

How to set up and validate locally

You may generate the fixtures and list them by running:

$ bundle exec rspec spec/frontend/fixtures/jobs.rb
$ ls tmp/tests/frontend/fixtures-ee/graphql/jobs/

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.