Add `plucky` to Ubuntu releases

[taylor.smock]

See testLatestUbuntuVersion.

We need to add 25.04 plucky to the repo.

We should probably drop the following:

• 23.04 lunar -- support ended 9 months ago
• 23.10 mantic -- support ended 3 months ago

The following are still supported:

• 18.04 bionic -- LTS support ended 1.5 years ago. Extended support will end in 3.5 years. It has Java 17 in repo. Default is Java 11.
  • sebastic recommends dropping support for anything outside of standard support, which would mean we drop 18.04 bionic as well.
  • We still support Java 11, and I don't think we need any "special" steps to support bionic, so leaving it for now is probably OK. We can drop it when we move to Java 17/21 as the minimum required version.
• 20.04 focal -- LTS support ends in 5 months, extended support ends in 5 years. It has Java 21 in repo. Default is Java 11.
• 22.04 jammy -- LTS support ends in 2.5 years, extended support ends in 7 years. Default is Java 11.
• 24.04 noble -- standard support ends in 4.5 years, LTS support ends in 4.5 years, extended support ends in 11 years. Default is Java 21.
• 24.10 oracular -- standard support ends in 8 months. Not LTS. Default is Java 21.

Note: I'll be copying this over (with modifications) to #17858.