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.c

@@ -93,23 +93,6 @@ int parse_ifindex(const char *s) {
         return ifi;
 }
 
-int parse_ifindex_or_ifname(const char *s) {
-        int r;
-
-        assert(s);
-
-        r = parse_ifindex(s);
-        if (r > 0)
-                return r;
-        assert(r < 0);
-
-        r = (int) if_nametoindex(s);
-        if (r <= 0)
-                return -errno;
-
-        return r;
-}
-
 int parse_mtu(int family, const char *s, uint32_t *ret) {
         uint64_t u;
         size_t m;