core -> metropolis

Smalltown is now called Metropolis!

This is the first commit in a series of cleanup commits that prepare us
for an open source release. This one just some Bazel packages around to
follow a stricter directory layout.

All of Metropolis now lives in `//metropolis`.

All of Metropolis Node code now lives in `//metropolis/node`.

All of the main /init now lives in `//m/n/core`.

All of the Kubernetes functionality/glue now lives in `//m/n/kubernetes`.

Next steps:
     - hunt down all references to Smalltown and replace them appropriately
     - narrow down visibility rules
     - document new code organization
     - move `//build/toolchain` to `//monogon/build/toolchain`
     - do another cleanup pass between `//golibs` and
       `//monogon/node/{core,common}`.
     - remove `//delta` and `//anubis`

Fixes T799.

Test Plan: Just a very large refactor. CI should help us out here.

Bug: T799

X-Origin-Diff: phab/D667
GitOrigin-RevId: 6029b8d4edc42325d50042596b639e8b122d0ded
diff --git a/metropolis/proto/common/BUILD.bazel b/metropolis/proto/common/BUILD.bazel
new file mode 100644
index 0000000..882bb61
--- /dev/null
+++ b/metropolis/proto/common/BUILD.bazel
@@ -0,0 +1,23 @@
+load("@rules_proto//proto:defs.bzl", "proto_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("@io_bazel_rules_go//proto:def.bzl", "go_proto_library")
+
+proto_library(
+    name = "common_proto",
+    srcs = ["common.proto"],
+    visibility = ["//visibility:public"],
+)
+
+go_proto_library(
+    name = "common_go_proto",
+    importpath = "git.monogon.dev/source/nexantic.git/metropolis/proto/common",
+    proto = ":common_proto",
+    visibility = ["//visibility:public"],
+)
+
+go_library(
+    name = "go_default_library",
+    embed = [":common_go_proto"],
+    importpath = "git.monogon.dev/source/nexantic.git/metropolis/proto/common",
+    visibility = ["//visibility:public"],
+)