Landlock Metadata Control

📧 Patch Set V3 (in review)

This series adds two new Landlock filesystem access rights, LANDLOCK_ACCESS_FS_READ_METADATA and LANDLOCK_ACCESS_FS_WRITE_METADATA, which control access to file and directory metadata such as inode attributes (mode, ownership, timestamps), extended attributes, POSIX ACLs and chattr(1)-style flags.