Clicking wallpaper thumbnails should download the full version.

[MatthewTighe]

If a wallpaper thumbnail isn't downloaded when clicked, it should be downloaded.

• When a wallpaper is clicked a loading indicator should be shown and the thumbnail opacity should be set to 50% while the wallpaper downloads.
• When a wallpaper is finished downloading it should be shown normally

Note: this is specifically for the settings page but should be done such that it can be easily copied into the upcoming wallpaper onboarding card. This means exposing a click handler or something similar so that the home screen can update its view with the newly selected wallpaper. This is dependent on #26211

┆Issue is synchronized with this Jira Task

[MatthewTighe]

Note that the underlying functionality to download a wallpaper on click will be added in https://github.com/mozilla-mobile/fenix/pull/26562/files

This ticket is about responding to changes in wallpaper.assetsFileState appropriately to show the loading indicator and opacity.

[delia-pop]

Verified as fixed on Nightly 107.0a1 from 09/20 with Google Pixel 6 (Android 13). When tapping on the wallpaper thumbnails, a loading indication is displayed and the thumbnail opacity changes during the download. The wallpaper is correctly displayed after download.

26212.mp4