Migrate to Node 20, clean up workflows (#2902)

Tests still appear to fail per #2898. Unfortunately, I need actions/runner#2347 to ignore the test failures properly - I need them to be warnings, not hard errors.

.github/workflows/push-master.yml

@@ -1,19 +1,17 @@
-name: 'Push `master`'
+name: Warn on pushing to `master`
 on:
   pull_request:
     types: [opened]
-    branches: ['master']
+    branches: [master]
+permissions:
+  issues: write
 jobs:
   comment:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/github-script@v3
-        with:
-          github-token: ${{secrets.GITHUB_TOKEN}}
-          script: |
-            await github.issues.createComment({
-              issue_number: context.issue.number,
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              body: `⚠⚠⚠ Hey @${context.actor}, did you mean to open this against \`next\`? ⚠⚠⚠`
-            })
+      - run: |
+          gh issue comment ${{ github.event.pull_request.url }} \
+            --body '⚠⚠⚠ Hey @${{ github.actor }}, did you mean to open this against `next`? ⚠⚠⚠'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        name: Post alert comment