Optimize journald for high throughput

Disable compression and sealing, disable rate limits.

Run a separate journald instance for nginx only, to allow scaling
to multiple cores (in case of DDoS).

roles/float-base/files/journald.conf

 [Journal]
 Storage=volatile
+RateLimitIntervalSec=0
+RateLimitBurst=0
+Compress=no
+Seal=no

roles/float-infra-nginx/templates/nginx.service.j2

@@ -36,5 +36,7 @@ AmbientCapabilities=CAP_NET_BIND_SERVICE
 RuntimeDirectory=nginx
 RuntimeDirectoryMode=750
 
+JournalNamespace=nginx
+
 [Install]
 WantedBy=multi-user.target