POS: Remove timeouts from PointOfSaleAggregateModelTests

[staskus]

Description

I checked the POS tests that we use timeouts, and noticed two in PointOfSaleAggregateModelTests.

As far as I understand, the complexity in these tests is related to the fact that we want to verify that collectPaymentWasCalled not when checkOut was called, but when the reader was connected.

I combined onCollectPaymentCalled callback and withCheckedContinuation to keep the same test logic but remove the timeouts.

Similar PR: #16210

Steps to reproduce

• CI should succeed

Screenshots

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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.

[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	pr16212-9ee2c4d
	Version	23.4
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	9ee2c4d
	Installation URL	5a3292viojefg

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

[joshheald]

Works well, thanks for the fix. I've checked that the final expectations are hit, and suggested some comment updates to keep the Given/When/Then syntax.

Thanks for sorting this