[Woo POS][Barcodes] Set up flow test failure screen

[joshheald]

Part of: WOOMOB-696

Description

This PR adds the error state for test scan's failing in the Star set up flow.

To do this, I've updated the flow definition to use a dictionary, rather than a linear array. Steps now define their own transitions.

In future, we may want an associated value on the error transition to pass different errors, but it might break the hashability and be a bit of a pain. We'll see if we need it, I don't want to over-complicate at the moment.

Steps to reproduce

1. Open POS, tap ... > Barcode scanning
2. Follow the Star flow
3. When asked to scan the test barcode, scan a different barcode instead.
4. Observe that you're shown the error.

Retry restarts the flow
Back takes you to the test page again.

Screenshots

error.flow.mp4

---

• 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	pr15903-8dd20c3
	Version	22.7
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	8dd20c3
	Installation URL	3r344tt8p9sv0

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

[staskus]

Thanks, I like the system. Looks simple enough and fitting for a few step flows.

[staskus]

I realized in the analytics PR as well that we need a strongly typed step definition. Therefore, it helps the analytics as well.