[Site design revamp] Use the custom Glide loader for preloading the thumbnails

[antonis]

Description

Wraps the thumbnail url String in an MShot object so that the retries are handled correctly when the server redirects to a loading gif image when the thumbnail is not ready. This is a continuation of the thumbnail preloading implementation from #16584

To test:

• Uninstall and reinstall the app or clear the app data from the Settings. You can try to fetch uncached MShots by changing the requested dimensions (hpp_layout_card_height, hpp_layout_card_width) or changing the interface language.
• Follow the instruction on [Site design revamp] Preload MShots when the site creation activity starts #16584 (comment)

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

[peril-wordpress-mobile]

You can test the changes on this Pull Request by downloading the APKs:

• Jetpack-pr-16624-build-124088.apk

• WordPress-pr-16624-build-124088.apk

[ovitrif]

Works great 🎉 I tested this with 4 languages: NL, IT, ES and EN after clearing the app cache from settings.

Thank you @antonis for the fix 🙇

🚀

[mkevins]

Thank you for tackling this Antonis!