Add performance tests for saveListElements

Add performance tests for CpsDataService methods:
- saveListElements
- saveListElementsBatch

Results show that saveListElementsBatch (used only by NCMP for
saving CM-handles) has extremely poor performance compared to
saveListElements, which is over 4x faster and uses less memory.

Issue-ID: CPS-2019
Signed-off-by: danielhanrahan <daniel.hanrahan@est.tech>
Change-Id: I89d634c69b3790f1e1a79e2ff5392db5a45c761b