[POS Refunds] Feature Flag

[toupper]

WOOMOB-1179

Description

With this PR we add a feature flag for the first iteration of the refunds project.

Test Steps

CI should run fine

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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.

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 23.8. This milestone is due in less than 2 days. Please make sure to get it merged by then or assign it to a milestone with a later deadline.

Generated by 🚫 Danger

[wpmobilebot]

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

	App Name	WooCommerce iOS Prototype
	Build Number	pr16406-132271d
	Version	23.7
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	132271d
	Installation URL	4ng01tpg5jmqg

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[iamgabrielma]

Looks good! CI jobs are stuck for some reason, I've tried to re-run them but got the same result, let's try again later.