Issue 51121 - Remove hardcoded changelog file name
    
    Bug Description:  There are several places in the code where
                      the new changelog name is just a hardcoded
                      string.  So if the name changes we will have
                      many places that need to be updated.
    
    Fix Description:  Use a "define" for the file name in the bdb code,
                      and in the changelog get get the filename from
                      backend ldbminfo.
    
                      Also extended the ldbminfo flags to include the
                      backend implementation.  This will be used as
                      we start to need a way t odetect what database
                      backend is in use.
    
    relates: https://pagure.io/389-ds-base/issue/51121
    
    Reviewed by: firstyear(Thanks!)