LU-10994 clio: remove cpo_own and cpo_disown

LU-10994 clio: remove cpo_own and cpo_disown

Remove the cpo_own and cpo_disown methods from struct
cl_page_operations. These methods were only implemented by the vvp
layer so they can be inlined into cl_page_own0() and
cl_page_disown(). Move most of vvp_page_discard() and all of
vvp_transient_page_discard() into cl_page_discard().

Lustre-change: https://review.whamcloud.com/47372
Lustre-commit: 81c6dc423ce4c62a64d328e49697d26194177f9f

Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I3f156d6ca3e4ea11c050b2addda38e84a84634b9
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54035
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>