LU-8066 exports: move procfs exports to debugfs

LU-8066 exports: move procfs exports to debugfs

The server side has a exports proc directory with several entries.
Upstreaming requires Lustre not to use the proc directory so
we can move the exports directory to debugfs. This is server side
so the root only issue should be limited. This step will make
more of the stats Netlink work much easier.

Change-Id: I73e38813f049cf563cdc7e277e4fadecd5a94e98
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/57013
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>