Break up the ProtoDatabasePerfTests.

This CL breaks up many larger tests into smaller tests that are less
likely to time out. Also reduced the amount of work particular tests
perform to further ensure no timeouts.

TBR=nyquist@chromium.org

Bug: 879922
Change-Id: I9591c9bd4f4308ce9eb183289d5c49c98df72b32
Reviewed-on: https://chromium-review.googlesource.com/1240127
Commit-Queue: Troy Hildebrandt <thildebr@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595122}