[SYSTEMDS-3959] Report an error when a federated worker cannot bind its port

[gaturchenko]

The command systemds WORKER 80505 terminated silently with exit code 0. There are 2 causes:

1. No range check for -w <port>
2. FederatedWorker.run() captured every exception in a catch-all. The same held for occupied and reserved ports, and for the -fedMonitoring backend

The following changes were implemented:

• PortUtils (new): shared port validation plus explainBindFailure, which turns terse socket errors into messages naming the port and the cause.
• DMLOptions: -w and -fedMonitoring reject non-integers and ports outside [1, 65535]. A missing (optional) -w argument now falls back to the default port instead of throwing NumberFormatException.
• FederatedWorker / FederatedMonitoringServer: reject out-of-range ports upfront, warn on reserved ports (< 1024), and throw bind failures as DMLRuntimeException after logging.
• bin/systemds: the duplicated WORKER/FEDMONITORING check is now one checkPort function with a range check and exit 1. Previously, an error was printed and the JVM was launched regardless.