fix: use SystemTime instead of Duration for Tain

refactor: create s6 module, split status and move tai

BREAKING CHANGE: add _ in names and reorder metrics

feat: add updownsince and readysince seconds

refactor: use ExitStatus for wstat's type

refactor: use BorrowedFd for locked and refactor

BREAKING CHANGE: make escape and SvStatus private

chore: initial commit