Move diff-range computation into utils #6147

Job	Run time
Ruby analysis (ubuntu-latest, default)	48s
Ruby analysis (macos-latest, linked)	51s
Ruby analysis (macos-latest, default)	53s
Ruby analysis (ubuntu-latest, linked)	56s
Ruby analysis (macos-latest, nightly-latest)	59s
Ruby analysis (ubuntu-latest, nightly-latest)	50s
	5m 17s

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