Migrate away from deprecated apt-key(8)

Use of apt-key(8) is deprecated and, will stop working in Debian 12 (Bookworm). Instead we should drop keys (gpg --armor --export) in /etc/apt/keyrings/ with the .asc filename extension.

This is a blocker for upgrading our infra to Bookworm, but it can be done whenever we want before that.

Steps to fix

• Restrict the Tails APT key to the Tails repo (puppet-tails!128 - merged)
• puppet-code!2+