CI: Automatically cancel non-generated workflows

Specify concurrency groups for non-generated workflows so we can cancel in-progress runs when new commits are pushed to a PR.

.github/workflows/python312-windows.yml

@@ -14,6 +14,10 @@ on:
     - cron: '0 0 * * 1'
   workflow_dispatch:
 
+concurrency:
+  cancel-in-progress: ${{ github.event_name == 'pull_request' || false }}
+  group: ${{ github.workflow }}-${{ github.ref }}
+
 defaults:
   run:
     shell: bash