chore: Significantly restructure folder layout

This moves the various projects from "type-based" folders (such as
"services" or "tools") into more appropriate semantic folders (such as
"nix", "ops" or "web").

Deprecated projects (nixcon-demo & gotest) which only existed for
testing/demonstration purposes have been removed.

(Note: *all* builds are broken with this commit)

infra/kubernetes/nginx/nginx.conf

@@ -1,59 +0,0 @@
-daemon off;
-worker_processes  1;
-error_log stderr;
-pid /run/nginx.pid;
-
-events {
-    worker_connections  1024;
-}
-
-http {
-    log_format json_combined escape=json
-    '{'
-        '"time_local":"$time_local",'
-        '"remote_addr":"$remote_addr",'
-        '"remote_user":"$remote_user",'
-        '"request":"$request",'
-        '"status": "$status",'
-        '"body_bytes_sent":"$body_bytes_sent",'
-        '"request_time":"$request_time",'
-        '"http_referrer":"$http_referer",'
-        '"http_user_agent":"$http_user_agent"'
-        '}';
-
-    access_log /dev/stdout json_combined;
-
-    sendfile        on;
-    keepalive_timeout  65;
-
-    server {
-        listen 80 default_server;
-        location / {
-            return 200 "ok";
-        }
-    }
-
-    server {
-        listen       80;
-        server_name  oslo.pub;
-
-        location / {
-            return 302 https://www.google.com/maps/d/viewer?mid=1pJIYY9cuEdt9DuMTbb4etBVq7hs;
-        }
-    }
-
-    server {
-        listen       80;
-        server_name  git.tazj.in;
-
-        # Static assets must always hit the root.
-        location ~ ^/(favicon\.ico|cgit\.(css|png))$ {
-           proxy_pass http://cgit;
-        }
-
-        # Everything else hits the depot directly.
-        location / {
-            proxy_pass http://cgit/cgit.cgi/depot/;
-        }
-    }
-}