LU-13055 doc: update changelog manpages

LU-13055 doc: update changelog manpages

Add lctl-changelog_register.8 and lctl-changelog_deregister.8
manpages and update lctl.8 manpage to refer to them.

Lustre-change: https://review.whamcloud.com/44022
Lustre-commit: 393885c027793d27ec948fd4fccb47aa530d2bf8

Fixes: 15305c3c3fe7 ("LU-12214 build: fix build without lustre_utils")
Test-Parameters: trivial
Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Change-Id: Ie41db630c72f61a884cd8000e0a4aeeb42ca60eb
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/46007
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>