feat: support updating a headline's cookie from multiple lists

[thuyen]

Summary

On master if a headline has multiple lists, the cookie is only updated for the current list. In emacs org, the cookie reflects information about all lists under the headline. This PR just makes it so.

Changes

On master the headline would show either 2/3 or 1/1 depending where the last update happens.

Checklist

I confirm that I have:

• Followed the
  Conventional Commits
  specification (e.g., feat: add new feature, fix: correct bug,
  docs: update documentation).
• My PR title also follows the conventional commits specification.
• Updated relevant documentation, if necessary.
• Thoroughly tested my changes.
• Added tests (if applicable) and verified existing tests pass with
  make test.
• Checked for breaking changes and documented them, if any.

[seflue]

While you're on it, have you considered to also implement #305? I am really missing that feature and already thought about implementing it myself, but never found the time to wrap my head around the cookie code. Looking at your code, it seems, that it has gotten simpler over the last two years due to some refactorings, so it might be worth a shot. 🙂

[thuyen]

While you're on it, have you considered to also implement #305? I am really missing that feature and already thought about implementing it myself, but never found the time to wrap my head around the cookie code. Looking at your code, it seems, that it has gotten simpler over the last two years due to some refactorings, so it might be worth a shot. 🙂

Let's see if #926 works.

[kristijanhusak]

Thanks!