third_party/go: pay off some technical debt and hide the bodies

This is an amalgamation of a handful of small changes to Go deps.
Notably:

 - we remove our opencensus-proto fork, use upstream, use exclude=src to
   fix the build
 - unvendorify some deps
 - bump io_rules_go to fix WKT resolution

Notably, we now do not have the 'protoc-gen-go' error when running
kubecfg/kubectl anymore.

Change-Id: I34fb9e78b2b12e4543142183d601d01987076f32
diff --git a/WORKSPACE b/WORKSPACE
index 6ecd658..ed9de43 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -40,10 +40,10 @@
 # Download Go/Gazelle rules
 http_archive(
     name = "io_bazel_rules_go",
-    sha256 = "6a68e269802911fa419abb940c850734086869d7fe9bc8e12aaf60a09641c818",
+    sha256 = "d1ffd055969c8f8d431e2d439813e42326961d0942bdf734d2c95dc30c369566",
     urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/rules_go/releases/download/v0.23.0/rules_go-v0.23.0.tar.gz",
-        "https://github.com/bazelbuild/rules_go/releases/download/v0.23.0/rules_go-v0.23.0.tar.gz",
+        "https://mirror.bazel.build/github.com/bazelbuild/rules_go/releases/download/v0.24.5/rules_go-v0.24.5.tar.gz",
+        "https://github.com/bazelbuild/rules_go/releases/download/v0.24.5/rules_go-v0.24.5.tar.gz",
     ],
 )
 http_archive(