LU-8066 nodemap: migrate to debugfs

LU-8066 nodemap: migrate to debugfs

The nodemap interface in proc is for administration purposes only
so we can safely move it to debugfs.

Test-Parameters: trivial testlist=sanity-sec
Change-Id: I0797bb79896ae5d9fa3bf9088b97b10505762565
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/57401
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>