go: re-do the entire thing

This is a mega-change, but attempting to split this up further is
probably not worth the effort.

Summary:

1. Bump up bazel, rules_go, and others.
2. Switch to new go target naming (bye bye go_default_library)
3. Move go deps to go.mod/go.sum, use make gazelle generate from that
4. Bump up Python deps a bit

And also whatever was required to actually get things to work - loads of
small useless changes.

Tested to work on NixOS and Ubuntu 20.04:

   $ bazel build //...
   $ bazel test //...

Change-Id: I8364bdaa1406b9ae4d0385a6b607f3e7989f98a9
Reviewed-on: https://gerrit.hackerspace.pl/c/hscloud/+/1583
Reviewed-by: q3k <q3k@hackerspace.pl>
diff --git a/go/statusz/BUILD.bazel b/go/statusz/BUILD.bazel
index 4434b95..9becefc 100644
--- a/go/statusz/BUILD.bazel
+++ b/go/statusz/BUILD.bazel
@@ -1,21 +1,21 @@
 load("@io_bazel_rules_go//go:def.bzl", "go_library")
 
 go_library(
-    name = "go_default_library",
+    name = "statusz",
     srcs = [
         "load.go",
         "statusz.go",
     ],
     importpath = "code.hackerspace.pl/hscloud/go/statusz",
     visibility = ["//visibility:public"],
-    deps = [
-        "@com_github_golang_glog//:go_default_library",
-        "@com_github_shirou_gopsutil//load:go_default_library",
-    ],
     x_defs = {
         "code.hackerspace.pl/hscloud/go/statusz.GitCommit": "{STABLE_GIT_COMMIT}",
         "code.hackerspace.pl/hscloud/go/statusz.GitVersion": "{STABLE_GIT_VERSION}",
         "code.hackerspace.pl/hscloud/go/statusz.Builder": "{STABLE_BUILDER}",
         "code.hackerspace.pl/hscloud/go/statusz.BuildTimestamp": "{BUILD_TIMESTAMP}",
     },
+    deps = [
+        "@com_github_golang_glog//:glog",
+        "@com_github_shirou_gopsutil//load",
+    ],
 )