metropolis/proto: add private

We add a new proto package, 'private'. This will hold all non-public
proto messages for the implementation of the cluster lifecyclce design
document.

We duplicate 'internal' for two reasons:

 - make it easier to port code accross to use the new protos/cluster
   code, while slowly phasing out protos/internal.
 - 'internal' was a poor name choice, as it's significant in Go path
   naming, and might cause some problems in the future. We have Bazel's
   visiblility mechanism to protect accidental use.

Test Plan: New proto, not yet used - see rest of stack.

X-Origin-Diff: phab/D732
GitOrigin-RevId: 15632353c46068b4f4c5025828c9c8459feaa335
diff --git a/metropolis/proto/api/configuration.proto b/metropolis/proto/api/configuration.proto
index 8c953ed..41e57d0 100644
--- a/metropolis/proto/api/configuration.proto
+++ b/metropolis/proto/api/configuration.proto
@@ -26,6 +26,7 @@
 // fw_cfg).
 message NodeParameters {
     message ClusterBootstrap {
+        bytes owner_public_key = 1;
     }
     message ClusterRegister {
     }