Add common_core_default_config_path() which resolves the correct knoe.cfg
path (k3d/k3s/gke) from KNOE_MODE/DEPLOYMENT_MODE/CLUSTER_ENV env vars,
falling back to the first cfg file found under conf/. Replaces the
hardcoded knoe.cfg reference in the config-loading comment.
Co-authored-by: Junie <junie@jetbrains.com>