Download mail in reverse UID order.
Download mail in reverse UID order.

Higher UIDs tend to be more recent mail, which we want to download
first. Looks like the original mail sync code did this, but I lost that
feature in my rewrite.

wakermahmud/sync-engine,jobscore/sync-engine,gale320/sync-engine,gale320/sync-engine,PriviPK/privipk-sync-engine,EthanBlackburn/sync-engine,ErinCall/sync-engine,PriviPK/privipk-sync-engine,rmasters/inbox,nylas/sync-engine,gale320/sync-engine,ErinCall/sync-engine,jobscore/sync-engine,EthanBlackburn/sync-engine,nylas/sync-engine,jobscore/sync-engine,gale320/sync-engine,PriviPK/privipk-sync-engine,ErinCall/sync-engine,EthanBlackburn/sync-engine,nylas/sync-engine,nylas/sync-engine,wakermahmud/sync-engine,jobscore/sync-engine,Eagles2F/sync-engine,wakermahmud/sync-engine,rmasters/inbox,rmasters/inbox,Eagles2F/sync-engine,rmasters/inbox,gale320/sync-engine,Eagles2F/sync-engine,EthanBlackburn/sync-engine,closeio/nylas,closeio/nylas,EthanBlackburn/sync-engine,wakermahmud/sync-engine,PriviPK/privipk-sync-engine,PriviPK/privipk-sync-engine,ErinCall/sync-engine,ErinCall/sync-engine,Eagles2F/sync-engine,closeio/nylas,Eagles2F/sync-engine,wakermahmud/sync-engine,closeio/nylas