sql: benchmarks for multi-span scan with limit
sql: benchmarks for multi-span scan with limit

The benchmarks use a table with 10 * 1000 rows. The query involves 4 spans of
1000 rows each, with the filter passing on only the first 10,30,50,70 rows
respectively.

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