Mini pipeline graph dropdown - 16px icon size

What does this MR do and why?

Resolves #365718 (closed)

Updates size of the ci-icon in the pipeline mini graph dropdown to 16px.

Note: I also took the opportunity to port some raw .scss over to util classes.

Screenshots or screen recordings

before	after

How to set up and validate locally

• Navigate to CI/CD >> Pipelines
• Click on a stage in any pipeline mini graph
• Inspect the dropdown with dev tools
• Insure that the ci icon is 16px and not 18px

MR acceptance checklist

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