xfs_io.8: rearrange command listings by section

xfs_io.8: rearrange command listings by section

Most of the commands listed under "OTHER COMMANDS" apply to files or
filesystems.  Create two new sections for that and populate them
appropriately.

Here's what moves:

fsmap: moves from file io commands to filesystem commands
utimes: moves from file io commands to file commands

>From the OTHER COMMANDS section:

lsattr/chattr: moves to file commands
flink: moves to file commands
stat/statx: moves to file commands
lsproj/chproj: moves to file commands
parent: moves to file commands
[gs]et_encpolicy: moves to file io commands
freeze/thaw: move to filesystem commands
inject: move to filesystem commands
resblks: move to filesystem commands
shutdown: move to filesystem commands
statfs: move to filesystem commands
label: move to filesystem commands

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
[sandeen: drop notion of file io commands]
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>