Use github actions to automark stale PRs (#47936)

About The Pull Request

Clarification that was brought to my attention:
the repo for this action defines it as without activity, so I assume literally any discussion/review is enough to bump and avoid the stale.

Considering this, it may be worth deploying an autocloser on PRs and an autolabeler on issues as well.

As title

Currently configured to mark PRs stale after 7 days. RED LABEL prs are exempt.

DOES NOT autoclose.

This is definitely a shift in how stale PRs are handled so this is a discussion thread at the same time as a pull request.

Message used:
This PR has been inactive for long enough to be automatically marked as stale. This means it is at risk of being closed by a maintainer if it is not updated or reviews are not addressed. If your PR is closed as stale, feel free to open a new one after dealing with the issues.

.github/workflows/stale.yml

@@ -0,0 +1,19 @@
+name: Mark stale issues and pull requests
+
+on:
+  schedule:
+  - cron: "0 0 * * *"
+
+jobs:
+  stale:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/stale@v1
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        stale-pr-message: "This PR has been inactive for long enough to be automatically marked as stale. This means it is at risk of being closed by a maintainer if it is not updated or reviews are not addressed. If your PR is closed as stale, feel free to open a new one after dealing with the issues. This may also be an indication that the maintainers do not have interest in this change, you can try to convince them otherwise, or persist in the doomed world you have created."
+        days-before-stale: 7
+        stale-pr-label: 'Stale'
+        exempt-pr-label: 'RED LABEL'