sys/vfs/hammer: Cleanup hammer_format_volume_header() prototype

sys/vfs/hammer: Cleanup hammer_format_volume_header() prototype

No functional changes, just remove some arguments that can be
dereferenced from other pointers since it has way too many args,
plus some refactoring to make it look more like newfs_hammer code
which basically does the same thing.

(It doesn't need to be a generic function by having these fileds
as different arguments. Formatting a volume within kernel space
is specific to this ioctl, and the original design was to format
volumes in userspace. It's also technically possible to implement
hammer volume-add|del mostly in userspace. In fact the current
kernel code which formats volumes looks pretty much identical to
what newfs_hammer does on formatting after below commits, which
is natural thing considering what these commands do.)

c7a9d2e sys/vfs/hammer: Remove hammer_iterate_l1l2_entries()
de75bb2 sys/vfs/hammer: Fix/rewrite hammer_free_freemap()
d8d6680 sys/vfs/hammer: Fix/rewrite hammer_format_freemap()
28cdb63 sys/vfs/hammer: Remove struct bigblock_stat
12d76ce sys/vfs/hammer: Remove hammer_test_free_freemap()
e2c5fb2 sys/vfs/hammer: Separate total/free big-block counting from formatting