fix: Ensure xrpld service directories exist at startup

The package tmpfiles config creates `/var/lib/xrpld` and `/var/log/xrpld`
during install, but those directories can still be removed or damaged
afterward. When that happens, xrpld fails later with less helpful path
creation errors, such as permission denied while opening the log path.

Have systemd create the default state and log directories whenever the
service starts. This keeps the packaged defaults self-healing. Operators
who configure custom paths are unaffected and the default directories may be
 unused and is harmless.

package/shared/xrpld.service

@@ -17,6 +17,8 @@ ProtectHome=true
 PrivateTmp=true
 User=xrpld
 Group=xrpld
+StateDirectory=xrpld
+LogsDirectory=xrpld
 LimitNOFILE=65536
 
 [Install]