UFS/FFS: Migrate to modern uintXX_t from u_intXX_t.
As per https://lists.freebsd.org/archives/freebsd-scsi/2023-July/000257.html
move to the modern uintXX_t. While here also migrate u_char to uint8_t.
Where other kernel interfaces allow, migrate u_long to uint64_t.
No functional changes intended.
MFC-after: 1 week
Sponsored-by: The FreeBSD Foundation