- What I did
Added a --dry-run option to lkt pkg build, the same way we have one for lkt build, which reports the docker build command equivalent.
It is not 100% correct or as useful as the lkt build one, for a few reasons:

• it prints the lines out to stdout, which already is kind of busy
• it is not json or yaml, which are structured and both human and machine readable, but rather the docker build commands
• lkt pkg build does not actually do docker build, but rather uses buildkit with a container as a driver. You cannot really replicate that simply with a single command-line

But it is a good start.

- How I did it
Added another dockerRunner implementation that is dryrun.

- How to verify it
Run it manually. This does not need testing, just that there are no regressions, for which CI is good enough.

- Description for the changelog

pkg build --dry-run