LU-10499 pcc: improve pcc-detach and man pages

LU-10499 pcc: improve pcc-detach and man pages

Improve "lfs pcc detach_fid" to have a "--mnt|-m" option to match
the corresponding option for "lfs pcc attach_fid".  There isn't
any reason that they should be different.

Separate lfs-pcc-attach.1 and lfs-pcc-detach.1 from the
lfs-pcc.1 man page and improve descriptions of these commands.
Add links for lfs-pcc-attach_fid.1 and lfs-pcc-detach_fid.1.

Describe fields in lfs-pcc-state.1.  Add lfs-pcc-delete.1 page.

EX-bug-id: EX-4006
Test-Parameters: trivial testlist=sanity-pcc
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ieff40b7b133aef64200a9a3f6c1a948d7c3ebbe5
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54454
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>