LU-13814 osc: add osc transient page ops

LU-13814 osc: add osc transient page ops

As part of gradually removing cl_pages for transient pages,
create a special set of OSC page operations for them.

This makes it easier to see what's left for transient pages
and focus on removing that.

Signed-off-by: Patrick Farrell <patrick.farrell@oracle.com>
Change-Id: I20bbe7535e8df223ec1fff9b940b3063fcc3f8d7
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52077
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Qian Yingjin <qian@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>