Clean up consensus etcd log output

Integrates our Zap logger into our etcd embedded instance to
clean up the logs. Split out from D497 (ex feature/kubelet).

Test Plan:
`bazel run //core/scripts:launch` no longer shows etcd JSON
output.

X-Origin-Diff: phab/D498
GitOrigin-RevId: 8df3b9c3edd20310079306479adfadf983af7da2
diff --git a/core/internal/consensus/BUILD.bazel b/core/internal/consensus/BUILD.bazel
index 53b118d..c8b2f25 100644
--- a/core/internal/consensus/BUILD.bazel
+++ b/core/internal/consensus/BUILD.bazel
@@ -19,5 +19,6 @@
         "@io_etcd_go_etcd//proxy/grpcproxy/adapter:go_default_library",
         "@org_golang_x_sys//unix:go_default_library",
         "@org_uber_go_zap//:go_default_library",
+        "@org_uber_go_zap//zapcore:go_default_library",
     ],
 )