This commit changes the uploads:secure_upload_analyse_and_update
and uploads:disable_secure_uploads to no longer rebake affected
posts inline. This just took way too long, and if the task stalled
you couldn't be sure if the rest of it completed.
Instead, we can update the baked_version of affected posts and
utilize our PeriodicalUpdates job to gradually rebake them. I added
warnings about increasing the site setting rebake_old_posts_count and
the global setting max_old_rebakes_per_15_minutes before doing this
as well.
For good measure, the affected post IDs are written to a JSON file too.
1a3b9a7352