Issue 51192 - Add option to reject internal unindexed searches
    
    Bug Description:  Some plugins can perform unindexed searches, and under the
                      right conditions this can cause problems like exhausting DB locks.
                      The setting "nsslapd-require-index" does not apply to internal
                      searches, so there is no way to prevent these searches from
                      occuring.
    
    Fix Description:  Add a new database setting "nsslapd-require-internalop-index"
                      that rejects an internal unindexed searches.
    
                      Also found during testing that when the RI plugin fails that
                      it does not set the proper result error code.
    
    relates: https://pagure.io/389-ds-base/issue/51192
    
    Reviewed by: firstyear, spichugi & tbordaz (Thanks!!!)