Resolve alternative ifnames wherever we would resolve an interface name

To keep the names manageable, "ifname_or_ifindex" is replaced by "interface".

src/basic/parse-util.h

@@ -14,7 +14,6 @@ int parse_dev(const char *s, dev_t *ret);
 int parse_pid(const char *s, pid_t* ret_pid);
 int parse_mode(const char *s, mode_t *ret);
 int parse_ifindex(const char *s);
-int parse_ifindex_or_ifname(const char *s);
 int parse_mtu(int family, const char *s, uint32_t *ret);
 
 int parse_size(const char *t, uint64_t base, uint64_t *size);