ci: add concurrency group to functions.yaml to cancel redundant runs (#3536)

* ci: add concurrency group to functions.yaml to cancel redundant runs

Without a concurrency configuration, pushing multiple commits to the
same PR triggers multiple simultaneous workflow runs. Add a concurrency
group keyed on workflow name and ref so that only the latest run for a
given branch or PR is active, cancelling any in-progress predecessor.

Fixes #3531

* ci: only cancel in-progress runs for PRs, not main pushes

Pushes to main trigger build and publish jobs. Cancelling an in-progress
main run when another push arrives could interrupt image publishing.
Make cancel-in-progress conditional on pull_request events only.

Author: Ankitsinghsisodya

.github/workflows/functions.yaml

@@ -16,6 +16,10 @@ on:
     branches:
       - main
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
 # Global version definitions
 env:
   PYTHON_VERSION: "3.10"