GH-48486: [GLib][Ruby] Add GArrowListFlattenOptions
Rationale for this change
The ListFlattenOptions class is not available in GLib/Ruby, and it is used together with the list_flatten compute function.
What changes are included in this PR?
This adds the ListFlattenOptions class to GLib.
Are these changes tested?
Yes, with Ruby unit tests.
Are there any user-facing changes?
Yes, a new class.
- GitHub Issue: #48486
:warning: GitHub issue #48486 has been automatically assigned in GitHub to PR creator.
@raulcd This is expected. I initially created one large PR to avoid conflicts, but @kou asked me to open separate PRs, see https://github.com/apache/arrow/pull/48357#issuecomment-3616543303.
Now that the PRs are already opened, I suggest that I rebase one every time one is merged, ok? I started with this one.
Thanks @stenlarsson for this work! That sounds good to me. Maybe you could mark them as draft so it's easier to find the one that is currently expected to be reviewed but as soon as you and @kou are happy with the approach to know the next one to review, that certainly works!