Wrap apt to download lists if there are none

An alternative to #12238 would be to get apt to download the lists of packages if there are none on the system.

It would have all the advantages of shipping the lists #12238 except saving download time to people with no persistent storage. Installing additional package is probably more rare for people who don’t have a persistent storage than for people who have one.

It would have none of the disadvantages of #12238:

• It’s not making our ISO image bigger.
• It’s not distributing outdated lists that might make people miss security upgrades.

User research findings

During the user testing of the Additional Software, all 5 participants ended up doing stuff on the command line. They were all using Linux as their regular operating system but their expertise on the command line ranged from Linux professional to basic copy-paster.

• 3 of them because it was instructed on the Mumble website. Probably many Linux applications do the same.
• 2 of them because they were used to doing that to install packages.

Related issues

• Related to #12238
• Related to #14544 (closed)