usr.sbin/makefs: Add HAMMER2 offline inode setcheck|setcomp support
This commit adds "setcheck" and "setcomp" commands to "-o I" option.
`image-file` argument is a valid HAMMER2 image file or block device.
`directory` argument is unused, but needs to be a valid path or "--".
e.g.
$ makefs -t hammer2 -o I=setcheck:/path/to/file:sha192 /dev/adx --
$ makefs -t hammer2 -o I=setcomp:/path/to/file:zlib:6 /path/to/hammer2.img --
"setcheck" takes `:<inode_path>:<check_algo>` string after command name.
"setcomp" takes `:<inode_path>:<comp_algo>[:<comp_level>]` string
after command name. These are equivalent to hammer2(8) setcheck and
setcomp directives.