Additional triage for packages that are obsolete but supported in LTS/ELTS

Cf. deblts-team@freexian.com thread "Obsolete packages triage/support" started 2023-03-02.

Brought to the attention of security team: https://lists.debian.org/debian-lts/2023/03/msg00036.html

Edit 2023-04-12: discussion with the security team is only for the LTS-specific part