Generate a manifest of packages used at build time

At ISO build time, generate a list of used packages and version, including packages used at build time but not shipped in the ISO.

Output: a machine-readable file that sums up all the information we’ll later need to create a tagged, partial snapshot of the APT repositories we use, that contains only packages that were used at ISO build time.

Blueprint: https://tails.boum.org/blueprint/freezable_APT_repository/

Feature Branch: feature/10748-gen-packages-manifest

Parent Task: #9489 (closed)

Related issues

• Related to #5548 (closed)
• Has duplicate #6297 (closed)
• Blocks #11412 (closed)

Original created by @intrigeri on 10748 (Redmine)