LU-17370 utils: simplify lfs-mirror-extend help text

LU-17370 utils: simplify lfs-mirror-extend help text

Add list of lfs setstripe command line options
to help text of lfs mirror extend.
Simplify syntax of lfs mirror extend help text.
Update corresponding lfs-mirror-extend man page.
On man pages make left side adjustment and disable hyphenation:
'.nh', '.ad l' to prevent hyphenation of keywords

Signed-off-by: Alexandre Ioffe <aioffe@ddn.com>
Test-Parameters: trivial
Change-Id: I6cffcdb9651062e169f53868827646b876a82cb5
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/53719
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>