kubectl: Allow []byte config fields to be set by the cli

Allows []byte config fields such as 'certificate-authority-data'
to be set using `kubectl config set` commands.

contrib/completions/bash/kubectl

@@ -3086,6 +3086,7 @@ _kubectl_config_set()
     flags_with_completion=()
     flags_completion=()
 
+    flags+=("--set-raw-bytes=")
     flags+=("--alsologtostderr")
     flags+=("--api-version=")
     flags+=("--as=")