subnet: dhcp: improve Net::IP usage

subnet: dhcp: improve Net::IP usage

This simplifies the comparison of IPs by using the object-oriented
interface over the procedural one. Also instantiate the ips using the
new method rather than using new, which isn't a keyword in Perl. This
fixes the respective perlcritic warning.

Signed-off-by: Stefan Hanreich <s.hanreich@proxmox.com>
Tested-by: Hannes Duerr <h.duerr@proxmox.com>
Link: https://lore.proxmox.com/20250307125056.169575-1-s.hanreich@proxmox.com
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>