EX-8688 csdc: Add header checksum verification and calculation

EX-8688 csdc: Add header checksum verification and calculation

This commit adds functionality to verify and calculate the checksum
of the header in the `ll_compr_hdr` struct and some another sanity
check.

Signed-off-by: Artem Blagodarenko <ablagodarenko@ddn.com>
Change-Id: I24a9ab9cb7bea1208ada23aa6550127fe6a55017
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/53521
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Vitaliy Kuznetsov <vkuznetsov@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>