ci: Use OIDC to log into Azure

This completely eliminates the Azure secret from the repo, following the below
guidance:

https://docs.github.com/en/actions/security-for-github-actions/security-hardening-your-deployments/configuring-openid-connect-in-azure

The federated identity is scoped to the `ci` environment, meaning:

 * I had to specify this environment in some YAMLs. I don't believe there's any
   downside to this.
 * As previously, the CI works seamlessly both from PRs and in the manual
   workflow.

I also deleted the tools/packaging/kata-deploy/action folder as it doesn't seem
to be used anymore, and it contains a reference to the secret.

Signed-off-by: Aurélien Bombo <abombo@microsoft.com>

tests/integration/kubernetes/gha-run.sh

@@ -567,7 +567,6 @@ function main() {
 
 	case "${action}" in
 		install-azure-cli) install_azure_cli ;;
-		login-azure) login_azure ;;
 		create-cluster) create_cluster "" ;;
 		create-cluster-kcli) create_cluster_kcli ;;
 		configure-snapshotter) configure_snapshotter ;;