storage: add more info to a raft truncation error message
storage: add more info to a raft truncation error message

This should help with #4890.

petermattis/cockroach,veteranlu/cockroach,bg451/cockroach,maxlang/cockroach,paperstreet/cockroach,glycerine/cockroach,sunya123/cockroach,arjun4084346/cockroach,paperstreet/cockroach,petermattis/cockroach,vaibhavarora/cockroach,nieyy/cockroach,arjun4084346/cockroach,bg451/cockroach,sunya123/cockroach,veteranlu/cockroach,arjun4084346/cockroach,vivekmenezes/cockroach,vivekmenezes/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,cockroachdb/cockroach,glycerine/cockroach,maxlang/cockroach,arjun4084346/cockroach,glycerine/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,maxlang/cockroach,glycerine/cockroach,veteranlu/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,glycerine/cockroach,nieyy/cockroach,maxlang/cockroach,glycerine/cockroach,vaibhavarora/cockroach,sunya123/cockroach,cockroachdb/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,bg451/cockroach,bg451/cockroach,veteranlu/cockroach,glycerine/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,nieyy/cockroach,cockroachdb/cockroach,maxlang/cockroach,nieyy/cockroach,petermattis/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,vivekmenezes/cockroach,maxlang/cockroach,nieyy/cockroach,petermattis/cockroach,bg451/cockroach,arjun4084346/cockroach,sunya123/cockroach,cockroachdb/cockroach,vivekmenezes/cockroach,sunya123/cockroach,veteranlu/cockroach,petermattis/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,vivekmenezes/cockroach,petermattis/cockroach,sunya123/cockroach,sunya123/cockroach,maxlang/cockroach,nieyy/cockroach,petermattis/cockroach,maxlang/cockroach,paperstreet/cockroach,nieyy/cockroach,glycerine/cockroach,petermattis/cockroach,sunya123/cockroach,arjun4084346/cockroach,bg451/cockroach,veteranlu/cockroach,bg451/cockroach,paperstreet/cockroach,arjun4084346/cockroach,nieyy/cockroach,vivekmenezes/cockroach,arjun4084346/cockroach,cockroachdb/cockroach