[Woo POS] Fix stores without the supported country/currency can still access POS

Closes: #14367

Why

When the POS payments onboarding feature flag is enabled, the site checks (country and currency) function isn't invoked because it's currently under the onboarding state publisher. Therefore, stores with unsupported country/currency can still access POS when the onboarding feature flag is enabled (false in production, so the issue isn't expected to affect production users).

How

First, test cases were added/updated so that the new cases with the payments onboarding feature flag fail without any changes. Then, the site checks are included as a filter on the returned published whenever the WC version or the remote feature flag changes.

Steps to reproduce

In wp-admin WC settings, set the country to be not in the US while the currency is USD
In the app, go to Menu --> the POS row should not appear. before this PR, the POS row appears shortly
In wp-admin WC settings, set the country back to the US
Relaunch the app (so that the site settings are refreshed), go to Menu --> the POS row should appear shortly
In wp-admin WC settings, set the currency to non-USD while the country is in the US
Relaunch the app, go to Menu --> the POS row should not appear
In wp-admin WC settings, set the currency back to USD
Relaunch the app, go to Menu --> the POS row should appear shortly

Testing information

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

Reviewer (or Author, in the case of optional code reviews):

Please make sure these conditions are met before approving the PR, or request changes if the PR needs improvement:

[x] 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.
[x] Ensure Adequate Unit Test Coverage: The changes are reasonably covered by unit tests or an explanation is provided in the PR description.
[x] Manual Testing: The author listed all the tests they ran, including smoke tests when needed (e.g., for refactorings). The reviewer confirmed that the PR works as expected on all devices (phone/tablet) and no regressions are added.6

	App Name	WooCommerce iOS
	Build Number	pr14383-1f02e51
	Version	21.1
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	1f02e51a4a700ddfe2dd72ee9cdad1ea5ac5b31e
	App Center Build	WooCommerce - Prototype Builds #11531

woocommerce / woocommerce-ios