Onboarding Improvements: persist the chosen site

[momo-ozawa]

Description

This PR fixes two issues found in Calls for Testing for 18.8

• After selecting site and starting a Quick Start, close the app and open it again. Some other site (maybe site selected before logout?) gets selected as your current site and QS is gone.
• Initial QS prompt content is not scaling with system font size.

Ref: p5T066-2Rr-p2#comment-10832

How to test

1. Do a fresh install of wpios
2. Login
3. On the Login Epilogue, choose a site
4. Change the system font size
5. ✅ The Quick Start prompt should be showing and the content should be scaled according to the selected font size
6. Tap on the "Show me around" button
7. Close the Quick Start checklist
8. Close, then reopen the app
9. ✅ The selected site on My Site should be the site you selected in step 3
10. ✅ The Quick Start items should be shown in the menu

Scaling font size

Persisting the selected site

Simulator.Screen.Recording.-.iPhone.13.-.2021-12-08.at.11.13.24.mp4

Regression Notes

1. Potential unintended areas of impact
   N/A

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

3. What automated tests I added (or what prevented me from doing so)
   N/A

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• 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.

[peril-wordpress-mobile]

You can trigger an installable build for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[mokagio]

@momo-ozawa this has been bundled as part of 18.8 beta 4 (18.8.0.4), which is currently building in CI.

Thanks for your work 🙌