stat-util: rename files_same() → inode_same()

Let's be more accurate about what this function does: it checks whether
the underlying reported inode is the same. Internally, this already uses
a better named stat_inode_same() call, hence let's similarly name the
wrapping function following the same logic.

Similar for files_same_at() and path_equal_or_same_files().

No code changes, just some renaming.

src/basic/socket-util.c

@@ -223,7 +223,7 @@ bool socket_address_equal(const SocketAddress *a, const SocketAddress *b) {
                         return false;
 
                 if (a->sockaddr.un.sun_path[0]) {
-                        if (!path_equal_or_files_same(a->sockaddr.un.sun_path, b->sockaddr.un.sun_path, 0))
+                        if (!path_equal_or_inode_same(a->sockaddr.un.sun_path, b->sockaddr.un.sun_path, 0))
                                 return false;
                 } else {
                         if (a->size != b->size)