erofs-utils: mkfs: add `--xattr-inode-digest` option

Based on the original Hongbo's version [1], it enables storing the
SHA-256 digest of each inode as an extended attribute, in preparation
for the upcoming page cache sharing feature.

Example usage:
 $ mkfs.erofs --xattr-inode-digest=trusted.erofs.fingerprint [-zlz4hc] foo.erofs foo/

[1] https://lore.kernel.org/r/20251118015849.228939-1-lihongbo22@huawei.com

Co-developed-by: Hongbo Li <lihongbo22@huawei.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Tested-by: Hongbo Li <lihongbo22@huawei.com>
Link: https://lore.kernel.org/r/20251229180646.3017326-4-hsiangkao@linux.alibaba.com
7 files changed