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 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.