Add daily image / release version information in changes files of daily image

[jkirk]

For every Grml daily ISO "changes" files changes-last-release.txt and changes-last-daily.txt files are generated, e.g. https://daily.grml.org/grml-full-amd64-testing/2025-12-11_04_03_11/grml-full-daily20251211build552testing-amd64-logs/

The files start with something like this:

------------------------------------------------------------------------
Generated by CI for job grml-full-amd64-testing d20251211b552
------------------------------------------------------------------------

Please add a line to indicate which daily image / release version was used to list the changes. Thx.