Migrate our infrastructure to Puppet 4

Originally created by @intrigeri on #11834 (Redmine)

On Stretch we won’t have Puppet 3, so we’ll have to migrate to Puppet 4.

Lots of interesting discussions on this topic have happened on https://bugs.debian.org/826551, including how to migrate an existing storedconfig database to PuppetDB. Since then, puppetdb made it into Debian.

See upstream’s upgrading checklist for details.

Subtasks

• #11833 (closed)
• #11835 (closed)
• #11836 (closed)
• #11837 (closed)
• #11838 (closed)
• #15490 (closed)
• #15492 (closed)
• #15493 (closed)
• #15555 (closed)

Related issues

• Related to #11543 (closed)
• Related to #15647 (closed)
• Related to #15650 (closed)
• Related to #16083 (closed)
• Blocks #13285 (closed)