Regenerate media thumbnails when importing any WordPress backup

[sejas]

• Solves https://github.com/Automattic/dotcom-forge/issues/8758

Proposed Changes

• It runs wp media regenerate --yes WP-CLI commands after importing a Jetpack, Local, Playground or .wpress backup, fixing the thumbnails in ``
• There is a new import step for Jetpack sites that say Regenerating media…
• Add tests for the new step

If we observe other backups do not include the thumbnails, we can execute the same command for other backup types.

Testing Instructions

• Download a Jetpack backup or .wpress from an atomic site with images. You can use the activity log for that.
• Run npm start
• Import that backup into a new site (Add new site button) or existing site (Import/Export tab)
• Observe there is a new last step says Regenerating media…
• Start the site and go to wp-admin
• Navigate to media
• Observe all the thumbnails are correctly visible

import.jetpack.backup.and.regenerate.media.mp4

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[wojtekn]

If we observe other backups do not include the thumbnails, we can execute the same command for other backup types.

I can't reproduce the issue for my blog's Jetpack Backup, but I can reproduce it for my .wpress backup. Can we run this consistently for all import formats?

[sejas]

@wojtekn I've updated it 79f03bf, now it should work also for .wpress
There was an error about wp-config.php no existing, but now it's fixed on f9cc231

[wojtekn]

It works well for all supported import types - thumbnails are visible in WP Admin for each site.