Improve CMD task for matrix strategy

[ihostage]

What the history? 📝

1. In 2022 we had a problem with reusable workflow and matrix strategy (link already is broken https://github.community/t/reusable-workflow-with-strategy-matrix/205676/6)
2. We implemented a special trick (Unify sbt-matrix.yml and sbt.yml into cmd.yml #19) in May 2022.
3. In August 2022 GitHub had solved this problem but we missed this news.

So, we can use out-of-the-box feature of GitHub actions now and dramatically simplify our CMD task. Current documentation about using reusable workflow with matrix is here https://docs.github.com/en/actions/sharing-automations/reusing-workflows#using-a-matrix-strategy-with-a-reusable-workflow

@mkurz WDYT?

PS: I checked a new version for our core repo 15163869490. Moreover, I think the summary page for action looks more compacted now.

[mkurz]

We can do that, just scrolling through it should be OK.

If you are 100% sure this works, please merge. (We can always roll back anyway)

3. In August 2022 GitHub had solved this problem but we missed this news.

I heard about that a couple of times actually when I was looking into some GitHub actions things but didn't look into it because things worked for us anyway.

Do you think now that GitHub allows us to call re-usable workflows in more depth that this somehow helps us to set up scheduled builds for the 3.0.x branch (started by the main branch actually).