Update - rebooted the system and had to an -
$ sudo ifdown eth0
 and then -
$ sudo ifup eth0
 and then these two things show up beautifully -
[$] sudo systemctl status systemd-networkd
[sudo] password for shirish: 
● systemd-networkd.service - Network Service
   Loaded: loaded (/lib/systemd/system/systemd-networkd.service; enabled; vendor preset: enabled)
   Active: active (running) since Mon 2016-11-07 20:44:52 IST; 5min ago
     Docs: man:systemd-networkd.service(8)
 Main PID: 764 (systemd-network)
   Status: "Processing requests..."
    Tasks: 1 (limit: 4915)
   CGroup: /system.slice/systemd-networkd.service
           └─764 /lib/systemd/systemd-networkd
[$] sudo systemctl status systemd-resolved
● systemd-resolved.service - Network Name Resolution
   Loaded: loaded (/lib/systemd/system/systemd-resolved.service; enabled; vendor preset: enabled)
  Drop-In: /lib/systemd/system/systemd-resolved.service.d
           └─resolvconf.conf
   Active: active (running) since Mon 2016-11-07 20:44:54 IST; 5min ago
     Docs: man:systemd-resolved.service(8)
           http://www.freedesktop.org/wiki/Software/systemd/resolved
           http://www.freedesktop.org/wiki/Software/systemd/writing-network-configuration-managers
           http://www.freedesktop.org/wiki/Software/systemd/writing-resolver-clients
  Process: 962 ExecStartPost=/bin/sh -c [ ! -e /run/resolvconf/enable-updates ] || echo "nameserver 127.0.0.53" | /sbin/resolvconf -a systemd-re
 Main PID: 896 (systemd-resolve)
   Status: "Processing requests..."
    Tasks: 1 (limit: 4915)
   CGroup: /system.slice/systemd-resolved.service
           └─896 /lib/systemd/systemd-resolved
 I guess this worked out. The system is a dated workstation and hence has no wireless networking chip either on the motherboard or support on the chip itself hence didn't do anything about wpa_supplicant.