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/path-util.h

@@ -77,7 +77,7 @@ static inline bool path_equal_filename(const char *a, const char *b) {
         return path_compare_filename(a, b) == 0;
 }
 
-bool path_equal_or_files_same(const char *a, const char *b, int flags);
+bool path_equal_or_inode_same(const char *a, const char *b, int flags);
 
 char* path_extend_internal(char **x, ...);
 #define path_extend(x, ...) path_extend_internal(x, __VA_ARGS__, POINTER_MAX)