.github: exempt milestoned issues from stale bot, stale after 45 days (#3652)

Milestone means triaged. Close message said 14 days; config is 7.

.github/workflows/stale.yml

@@ -14,14 +14,16 @@ jobs:
     steps:
       - uses: actions/stale@4391f3da665fdf50b6810c1a66712fb9ba21aa93 # v11.0.0
         with:
-          days-before-issue-stale: 90
+          days-before-issue-stale: 45
           days-before-issue-close: 7
           stale-issue-label: "stale"
-          stale-issue-message: "This issue is stale because it has been open for 90 days with no
+          stale-issue-message: "This issue is stale because it has been open for 45 days with no
             activity."
-          close-issue-message: "This issue was closed because it has been inactive for 14 days
+          close-issue-message: "This issue was closed because it has been inactive for 7 days
             since being marked as stale."
           days-before-pr-stale: -1
           days-before-pr-close: -1
           exempt-issue-labels: "no-stale-bot,needs-more-info"
+          # A milestone means the issue is triaged; only untriaged issues go stale.
+          exempt-all-issue-milestones: true
           repo-token: ${{ secrets.GITHUB_TOKEN }}