Extend retention period for dist-artifacts

[xnyo]

dist-artifacts (built plugin) has a retention period of 7 days:

plugin-ci-workflows/.github/workflows/ci.yml

Line 421 in 2d617a5

retention-days: 7

This artifact is used for GCS upload and, more importantly e2e tests.

This can cause issue if the workflow fails and the failing steps are re-run after 7 days (especially for the e2e tests, which are prone to failing).

For example: https://github.com/grafana/grafana-dbo11y-app/actions/runs/17735353829/job/51204238118

The workaround is retrying the workflow from start to finish, which will force the plugin to be re-built and re-uploaded (so reset the retention period). However, the retention period should be extended to allow retrying e2e tests after 7 days from the original workflow run. It would also be nice to print a message explaining that the workflow should be re-run instead of this generic Artifact not found for name message, which is not clear.

Slack thread with more details: https://raintank-corp.slack.com/archives/C01C4K8DETW/p1758782856322209

[tolzhabayev]

It might make sense to make this an input with the default of 10 days and let projects that need the longer retention to configure it themselves