Confirm matching benchmark parameters

[agorrod]

We should confirm that equivalent parameters to the RocksDB and WiredTiger benchmarks result in similar behavior. RocksDB also allows many more configuration options - we should consider whether there is value in exposing such configuration options via the WiredTiger benchmark implementation as well.

[agorrod]

The specific configuration options aren't supported by WiredTiger and may be of interest are: universal_max_merge_width, universal_min_merge_width, level0_file_num_compaction_trigger and level0_slowdown_writes_trigger.