[META] Database Backup/Redundancy Improvements

Goals:

• Faster/More Frequent Staging Refreshes (#2718 (moved))
• Improve SLA numbers
• Automate automate automate
• Security security dsecurity

Track various proposed backup improvements

• Documented SLA
• Automated Restore Tests (#2709 (closed) and #1265 (moved))
• Time-Delayed Standby #2722 (moved)
• Logical replica
• Replace WAL-E (#2721 (closed))
• Change replication auth from password to something else, probably SSL cert
• More reliable replication lag monitoring
• Use local Azure blob storage instead of AWS S3 when running on Azure
• Use a disk for WAL for backups instead of tar files in blobs so it can be snapshotted and mounted directly?
• Use LVM or Azure snapshots for backups instead of tar?

c.f. BAD: #2671 (closed) and !346 and