ci: gate testing image publish on testing release

Author: nvasiu

.github/workflows/ecr-release.yml

@@ -14,6 +14,8 @@ env:
 
 jobs:
   build-and-upload-image-to-ecr:
+    # Only publish when the release includes a new testing package version.
+    if: contains(github.event.release.tag_name, 'testing-v')
     runs-on: ubuntu-latest
     permissions:
       contents: read