`NodeReachable`, `NodeLive`, `NodeSchedulable`, and `NodeRunnable` are mentioned
as "built-in set of conditions" but some of them do not exist in the current API.
Updated `pkgs/apis/core/types.go` too for consistency.
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>