DS-4194 Use lazy fetching iterator for long query results

[AndrewZachWood]

Solves: DS-4194

This moves away from reading every result into memory during the Discovery indexing process.

[tdonohue]

NOTE: This only affects master (pre-7.0) as the behavior seems to have changed after we did Hibernate deprecation fixes in #2111. So, this PR seems to be fixing an accidental side-effect of #2111.

[terrywbrady]

The performance gains are clear even with only 2000 or 4000 items.

2345 Items ======================

$ time winpty docker exec -it dspace //dspace/bin/dspace index-discovery -b -f

real    1m39.683s
user    0m0.000s
sys     0m0.015s

$ time winpty docker exec -it dspace //dspace/bin/dspace index-discovery -b -f

real    2m15.639s
user    0m0.031s
sys     0m0.015s

-----with new code

$ time winpty docker exec -it dspace //dspace/bin/dspace index-discovery -b -f

real    1m16.617s
user    0m0.000s
sys     0m0.046s

$ time winpty docker exec -it dspace //dspace/bin/dspace index-discovery -b -f

real    0m54.334s
user    0m0.015s
sys     0m0.046s

4343 items ===========================================


$ time winpty docker exec -it dspace //dspace/bin/dspace index-discovery -b -f

real    3m40.467s
user    0m0.015s
sys     0m0.046s

$ time winpty docker exec -it dspace //dspace/bin/dspace index-discovery -b -f

real    3m2.371s
user    0m0.000s
sys     0m0.046s


-------- with new code

$ time winpty docker exec -it dspace //dspace/bin/dspace index-discovery -b -f

real    1m27.602s
user    0m0.000s
sys     0m0.046s

$ time winpty docker exec -it dspace //dspace/bin/dspace index-discovery -b -f

real    1m26.785s
user    0m0.000s
sys     0m0.046s

[tdonohue]

Thanks for the testing, @terrywbrady !

👍 These code changes look good to me. I was just waiting on a verification test.

[tdonohue]

Thanks @AndrewZWood !