refactor: extract EnableV2ForTest helper to reduce flag toggle boilerplate #924

Job	Run time
Mac / integration (bdstore)	0s
Mac / integration (packages)	0s
Mac regression summary	0s
Mac / test-cover	0s
Mac / make test	0s
Mac / integration (rest)	0s
Mac / quality (lint, fmt, vet, docs)	-5s
Mac / acceptance (Tier A)	-7s
Mac / integration (review-formulas)	-9s
	-21s

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