These functions will take either an IPv4/IPv6 address, or an IPv4/IPv6
prefix, and cast them to their canonical form. Notably for IPv6 addresses,
this means lower case and with the 0-tuples correctly formatted:
2001:DB8::1 becomes 2001:db8::1
2001:db8:0:0::1 becomes 2001:db8::1
This avoids spurious diffs in vppcfg when comparing to the output of the VPP
dataplane.