Implement underestimatedCount for Product2Sequence #7

Job	Run time
Validate Format Config	10s
Test / Linux (5.8 - jammy)	39s
Test / Windows (5.9 - windows-2022)	11m 16s
Test / Linux (5.9 - jammy)	47s
Test / Windows (6.0 - windows-2022)	14m 40s
Test / Windows (nightly - windows-2019)	9m 42s
Test / Linux (5.10 - jammy)	44s
Test / Windows (nightly-6.1 - windows-2019)	9m 0s
Test / Linux (6.0 - jammy)	58s
Test / Linux (nightly-main - jammy)	1m 7s
Test / Linux (nightly-6.1 - jammy)	1m 1s
Soundness / Broken symlinks check	2s
Soundness / Documentation check	1m 8s
Soundness / API breakage check	44s
Soundness / Format check	38s
Soundness / License headers check	3s
Soundness / Python lint check	3s
Soundness / Shell check	31s
Soundness / Unacceptable language check	2s
Soundness / YAML lint check	6s
	53m 21s

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