Improve plans in site creation flow

[irfano]

This fixes some issues and improves the code from #19304

• 28e9a69: The plan selection screen was passing the domain from the redirect URL. However, this was incorrect because if a free domain is chosen, there is no paid_domain_name parameter in the redirect URL. Therefore, I used the viewmodel's domain name to pass it to the next screen.
• 342ec70: Fixed a wrong error message.
• 02bc3a2: Moved appendQueryParameter into already opened apply scope.
• 696dd82: The plan_id and plan_slug parameters were unnecessary when loading the plan selection link; they are being used only in redirect URLs.

To test:

Site creation with a free domain and free plan

1. Launch JP app
2. Go to Me-> Debug settings
3. Switch to the Remote Feature tab, find plans_in_site_creation, and enable it
4. Switch to My Site tab
5. Tap the down arrow to the right of the site name on the My Site screen
6. Tap the + icon at the top right on the Site picker screen
7. Select ⊕ Create WordPress.com site on the modal dialog
8. Tap Skip at the top right on the first step (topic screen)
9. Tap Skip at the top right on the next step (theme screen)
10. Enter a search query (whatever you want here)
11. Verify that the result domains are as shown in the screenshot above
12. Select a free domain (should be *.wordpress.com)
13. Verify Plans screen opens with Personal, Premium, Business, and Ecommerce plans
14. Select the free plan
15. Verify it returns to the site setup screen
16. Verify a site is created with the desired domain

Regression Notes

1. Potential unintended areas of impact
   This may affect the plan selection screen in the site creation flow.

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   Tested manually.

3. What automated tests I added (or what prevented me from doing so)
   I haven't added any automated test since this is an improvement PR for another PR.

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

UI Changes testing checklist:

• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• Talkback.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• Large and small screen sizes. (Tablet and smaller phones)
• Multi-tasking: Split screen and Pop-up view. (Android 10 or higher)

[peril-wordpress-mobile]

	Warnings
⚠️	This PR is assigned to a milestone which is closing in less than 4 days Please, make sure to get it merged by then or assign it to a later expiring milestone

Generated by 🚫 dangerJS

[wpmobilebot]

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

	App Name	Jetpack
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr19377-fc98307
	Commit	fc98307
	Direct Download	jetpack-prototype-build-pr19377-fc98307.apk

Note: Google Login is not supported on these builds.

[wpmobilebot]

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

	App Name	WordPress
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr19377-fc98307
	Commit	fc98307
	Direct Download	wordpress-prototype-build-pr19377-fc98307.apk

Note: Google Login is not supported on these builds.

[ravishanker]

Thanks for taking care of this 👍

Fixed an issue with flow steps, with plans appearing even when feature is not enabled.