Provide support for cache_from and cache_to fields

[flixman]

Currently the fields cache_from and cache_to on the build are ignored. This PR provides support for them in the build block, just by propagating them to the call to podman.

[p12tic]

Thanks for the PR. It looks good in principle.

What's missing:

• unit tests. I did some refactoring and added unit tests for image building functionality in Add unit tests for image building  #1094
• release note. Please see newsfragments/README.txt file

Also, podman build documentation says that cache-from is ignored unless --layers is specified. I suppose this PR won't do what user expects as is, what am I missing?

[p12tic]

Also, please rebase instead of merging main, thanks!

[flixman]

@p12tic About the --layers flag: I also saw the documentation, but I made a couple of tests and caches are used regardless on --layers being set or not. I have just reported this to podman, because looks like might be an error on the documentation.

[flixman]

@p12tic about the branch update (merging vs rebasing): Can't the "update with merge" be disabled on the GH UI? I just clicked on "update" and it did a merge. Now I have seen I had the option to "update with rebase", but if that is not valid... maybe should just not appear at all?

[p12tic]

Can't the "update with merge" be disabled on the GH UI? I just clicked on "update" and it did a merge.

Unfortunately github UI does not support this. They have different options for actual merging, but for the update button - no.

[p12tic]

Still needs a release note.

• release note. Please see newsfragments/README.txt file

[flixman]

Gosh, too many holidays. Done!