Convert version comparison tests to swift testing

[joshheald]

Description

Because the 9.6.0-beta woo builds weren't showing as eligible for POS, I investigated the version compare algorithm.

It is working correctly, we should have specified 9.6.0-beta as the minimum, not 9.6.0.

While I was investigating, I improved the tests by moving them to swift testing, and adding a comment which explains any failures; previously when there were failures it wouldn't tell you why.

Testing information

No code changes, just check the tests pass.

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

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• The PR is small and has a clear, single focus, or a valid explanation is provided in the description. If needed, please request to split it into smaller PRs.
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[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce iOS by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS
	Build Number	pr14947-3185c7f
	Version	21.4
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	3185c7f
	App Center Build	WooCommerce - Prototype Builds #12649

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[staskus]

Thanks for the improvement!

It is working correctly, we should have specified 9.6.0-beta as the minimum, not 9.6.0.

9.6.0-beta being considered below 9.6.0 makes so much sense but I haven't thought our checks work this way. A good learning 👍