[Woo POS] Show payment method name in success screen

[joshheald]

Closes: #15011

Description

This PR adds cash or card in the payment success screen, appropriate for whichever payment method was used.

The new payment method enum could be used in future to improve our state management – i.e. we could keep hold of the card payment state even when we go to cash, and use the payment method enum to declare which is the active payment method.

Steps to reproduce

1. Launch the app and open POS
2. Add items and check out
3. Take a payment

Observe that the success screen shows the payment method in the message.

Testing information

Screenshots

show.payment.method.in.success.screen.mp4

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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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[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	pr15030-49d20e3
	Version	21.5
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	49d20e3
	App Center Build	WooCommerce - Prototype Builds #12751

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[iamgabrielma]

Thanks for adding this! LGTM