Fix stale action to work repository-wide

[Okabe-Junya]

The stale action is currently non-functional due to a configuration conflict:

• only-labels: 'lang/es' requires items to have this label
• exempt-issue-labels: 'maintainers, lang/es' exempts items with this label

This results in all issues/PRs being skipped.

Background

• The action was originally designed for Spanish localization only (PR feat: stale issues and PR with not activity #1612)
• However, having repository-wide stale management would help keep issues and PRs actively maintained
• The current conflicting configuration should be fixed regardless of scope

Proposal

Expand the stale action to cover all issues and PRs by removing the only-labels restriction.

Open Questions

• Which labels should be exempt from stale processing?
• Should localization branches have separate stale policies?

[jihoon-seo]

My opinion is:

• The action is just to add a stale label (and not closing issues/PRs), so applying to all issues/PRs (including maintainers ones) would be okay. It will give us an visual notification for us that the issues/PRs got stale.
• It would be okay to single policy that covers all L10n branches, but we also can ask each team about their opinion.

[Okabe-Junya]

Thank you for your comment, and sorry for the confusion

In my understanding, actions/stale will "close" stale issues/prs as "not planed". So my question is "Should we automatically close all inactive issues/PRs (including l10n)?"
I think it's similar to Kubernetes (Prow) lifecycle labels.

glossary/.github/workflows/stale.yml

Line 40 in 48f411d

days-before-close: 20

[jihoon-seo]

Then, since the number of open issues and PRs in the Cloud Native Glossary repo is not that huge yet, I think it would be better to just add a label to the stale ones instead of closing them.
I would love to hear others' opinion too.