Purge Jessie time-based APT snapshots

Originally created by @intrigeri on #11912 (Redmine)

Related issues

• Related to #12605 (closed)
• Related to tails#12096 (closed)
• Related to #13526 (closed)
• Blocked by tails#10289 (closed)
• Blocks #13233 (closed)
• Blocked by tails#11738 (closed)