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/dc/arista-proxy/main.go b/dc/arista-proxy/main.go
index ed4a9b3..15c9262 100644
--- a/dc/arista-proxy/main.go
+++ b/dc/arista-proxy/main.go
@@ -6,7 +6,7 @@
 
 	"code.hackerspace.pl/hscloud/go/mirko"
 	"github.com/golang/glog"
-	"github.com/q3k/cursedjsonrpc"
+	cursedjsonrpc "github.com/q3k/cursedjsonrpc"
 
 	pb "code.hackerspace.pl/hscloud/dc/arista-proxy/proto"
 )