erofs-utils: mkfs: support `-Efragdedupe=inode`

erofs-utils: mkfs: support `-Efragdedupe=inode`

If the entire inode can be deduplicated against an existing fragment,
simply reuse it.

Multi-threading can still be applied for `-Efragdedupe=inode` with
the current codebase:

Fedora Linux 39 (Workstation Edition) LiveCD results:
 -zlzma,level=6,dictsize=131072 -C65536 -Eall-fragments

   `-E^fragdedupe`         2,003,587,072 bytes (1911 MiB)
   `-Efragdedupe=inode`    1,970,577,408 bytes (1880 MiB)

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250103024011.198163-1-hsiangkao@linux.alibaba.com