Speed up CI/CD Pipeline

[wr1159]

Summary

Add yarn cache into pipeline

Changes

• Use yarn cache in pipeline
• Merged build and test stage
• Should speed up the pipeline by about 5 minutes

Checklist

• [x] Test coverage has not deteriorated
• [x] CI is green
• [x] Added hours into project log
• [x] Strikethrough in sprint google slides.

[github-actions[bot]]

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