Ticket 48864 - Cleanup memory detection before we add cgroup support
    
    Bug Description:  Our old memory detection code was really spaghetti
    like, and not very nice. Make a cleaner better interface.
    
    Fix Description:  Add a new slapi platform abstraction. We will start
    to move pieces of abstraction in here as needed.
    
    This contains a struct of system information such an memory infomation.
    due to the design, we can now test not only the memory detection, but
    because we pass mi as a parameter to util_cachesize_issane, we can
    now test our cache checking function too.
    
    https://pagure.io/389-ds-base/issue/48864
    
    Author: wibrown
    
    Review by: mreynolds (Thanks!)