chore: Use pull request number for workflow concurrency groups.

Author: ricogu

.github/workflows/build-and-test.yml

@@ -10,7 +10,7 @@ on:
       - reopened
 
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
   cancel-in-progress: true
 
 jobs: