ci: cancel previous runs on PR push

After this patch, current PR pipeline runs will be cancelled if new
commits/force push triggers new pipelines.

Author: DifferentialOrange

.github/workflows/packing.yml

@@ -6,6 +6,10 @@ on:
   pull_request_target:
     types: [labeled]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   pack_pip:
     # We want to run on external PRs, but not on our own internal

.github/workflows/testing.yml

@@ -6,6 +6,10 @@ on:
   pull_request_target:
     types: [labeled]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   run_tests_ce_linux:
     # We want to run on external PRs, but not on our own internal