Rebase to btrfs 5.16.1, changes below:

• mkfs: support DUP on metadata on zoned devices
• subvol delete: drop warning for root when search ioctl fails
• check:
• fix --init-csum-tree to not create checksums for extents that are not supposed to have them
• add check for metadata item levels
• add udev rule for zoned devices as they require mq-deadline
• rescue: new subcommand clear-uuid-tree to fix failed mount due to bad uuid subvolume keys, caught by tree-checker
• fi du: skip inaccessible files
• prop: properly resolve to symlink targets
• send, receive: fix crash after parent subvolume lookup errors
• build:
• fix redefinition of ALIGN on mixed old/new kernel/userspace (5.11)
• fix build on 5.12+ kernels due to changes in linux/kernel.h
• fix build on musl with old kernel headers
• other:
• typo fixes
• new tests
• CI targets updated
• error handling fixes, cleanups, refactoring
• extent tree v2 preparatory work
• lots of RST documentation updates (last release with asciidoc sources), https://btrfs.readthedocs.io