pkg/kubeapply: Clean up the phase-ordering code
pkg/kubeapply: Clean up the phase-ordering code

 - Don't treat "last" so specially; we can code it as an ordinary phase
   prefix.
 - Taking a byte and casting it to a rune, then calling unicode.IsDigit
   isn't actually Unicode-safe.  Since we're assuming byte-oriented text
   anyway, just do an ASCII ('0' <= c && c <= '9') check.
 - Improve naming

datawire/ambassador,datawire/telepresence,datawire/ambassador,datawire/ambassador,datawire/ambassador,datawire/telepresence,datawire/ambassador,datawire/telepresence