Ticket 51175 - resolve plugin name leaking
    
    Bug Description: Previously pblock.c assumed that all plugin
    names were static c strings. Rust can't create static C
    strings, so these were intentionally leaked.
    
    Fix Description: Rather than leak these, we do a dup/free
    through the slapiplugin struct instead, meaning we can use
    ephemeral, and properly managed strings in rust. This does not
    affect any other existing code which will still handle the
    static strings correctly.
    
    https://pagure.io/389-ds-base/issue/51175
    
    Author: William Brown <william@blackhats.net.au>
    
    Review by: mreynolds, tbordaz (Thanks!)