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/bgpwtf/invoice/proto/BUILD.bazel b/bgpwtf/invoice/proto/BUILD.bazel
index a1a7033..6eff00e 100644
--- a/bgpwtf/invoice/proto/BUILD.bazel
+++ b/bgpwtf/invoice/proto/BUILD.bazel
@@ -20,7 +20,7 @@
 )
 
 go_library(
-    name = "go_default_library",
+    name = "proto",
     embed = [":proto_go_proto"],
     importpath = "code.hackerspace.pl/hscloud/bgpwtf/invoice/proto",
     visibility = ["//visibility:public"],