puppet_enterprise::repo::config needs to use modern APT keyrings

[kenyon]

(Previously filed as https://puppet.atlassian.net/browse/ENTERPRISE-1512)

Use Case

Debian-family operating systems have deprecated the direct usage of apt-key for several years now. apt-key add installs GPG keys into /etc/apt/trusted.gpg or /etc/apt/trusted.gpg.d. Installing keys there causes warnings on Ubuntu 22.04 when running apt update. This will become an error in Ubuntu 24.04. puppetlabs-apt v9.2.0 supports modern APT keyrings so you can see how it's done, since puppet_enterprise::repo::config installs the PE key manually: puppetlabs/puppetlabs-apt#1150

Describe the Solution You Would Like

puppet_enterprise::repo::config should place the PE GPG key in the /etc/apt/keyrings directory, and add signed-by=/etc/apt/keyrings/pe.asc to the sources.list file that puppet_enterprise::repo::config creates. Or just use the puppetlabs-apt module. Example: puppetlabs/puppetlabs-puppet_agent#681

Describe Alternatives You've Considered

There isn't really an alternative, this has to be done for Ubuntu 24.04, and should be done for Ubuntu 22.04.

[github-actions]

Migrated issue to PE-37301

[GSPatton]

Hi @kenyon. Thanks for this! I'll work on getting this prioritised and into the right hands