chore: optimize Argos CI setup (#9115)

.github/workflows/argos.yml

@@ -5,9 +5,25 @@ on:
     branches: [main]
   pull_request:
     branches: [main]
+    types:
+      # Those 3 are the default PR workflow activity types,
+      # see https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request
+      - opened
+      - synchronize
+      - reopened
+      # We want trigger workflow on labeled too!
+      - labeled
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
 
 jobs:
   take-screenshots:
+    # Argos is heavy to run
+    # We only want to trigger Argos on PRs with the 'Argos' label
+    # See https://stackoverflow.com/questions/62325286/run-github-actions-when-pull-requests-have-a-specific-label
+    if: ${{ github.ref_name == 'main' || (github.event_name == 'pull_request' && contains(github.event.pull_request.labels.*.name, 'Argos')) }}
     runs-on: ubuntu-latest
     steps:
       - name: Check out repository code