[Containerapp] az containerapp sessionpool update: Fix updating registry credentials with --registry-username and --registry-password when existing registry credentials are empty#8483

zhoxing-ms merged 7 commits intoAzure:mainAzure/azure-cli-extensions:mainfrom

Greedygre:xinyu/20250213_fix_sessionpool_registry_credentical_updateGreedygre/azure-cli-extensions:xinyu/20250213_fix_sessionpool_registry_credentical_updateCopy head branch name to clipboard