kdump-lib: Harden _crashkernel_add
    
    Resolves: https://issues.redhat.com/browse/RHEL-8727
    Resolves: https://issues.redhat.com/browse/RHEL-8710
    Upstream: Fedora
    Conflict: spec/kdump-lib_spec.sh doesn't exist in RHEL, so I remove
              the hunk directly.
    
    commit 64f2827a4bfa3f26974972f2f5a4477eec58f221
    Author: Philipp Rudo <prudo@redhat.com>
    Date:   Wed Sep 6 10:49:47 2023 +0200
    
        kdump-lib: Harden _crashkernel_add
    
        _crashkernel_add currently always assumes the good case, i.e. that the
        value of the crashkernel parameter has the correct syntax and that the
        delta added is a number. Both doesn't have to be true when the values
        are provided by users. Thus add some additional checks.
    
        Furthermore require the delta to have a explicit unit, i.e. no longer
        assume that is in megabytes, i.e. 100 -> 100M.
    
        Signed-off-by: Philipp Rudo <prudo@redhat.com>
        Reviewed-by: Pingfan Liu <piliu@redhat.com>
    Signed-off-by: Baoquan He <bhe@redhat.com>