[release-3.5] Fix the issue that learner promotion command doesn't support json output#19602

ahrtr merged 2 commits intoetcd-io:release-3.5etcd-io/etcd:release-3.5from

ahrtr:3.5_add_learner_test_20250314ahrtr/etcd:3.5_add_learner_test_20250314Copy head branch name to clipboard