Benchmark SS

[alexanderbez]

Each SS backend engine should be benchmarked using a large enough and consistent data set, preferably one we use for SC as well.

In addition, for each backend engine (RocksDB, PebbleDB, BTree/SQLite), ensure the default configurations are evaluated correctly.

[alexanderbez]

I'm going to mark #17280 as closing this. We have baseline benchmarks and we can use them to add further benchmarks (just by updating the engines map) to further benchmarks the existing engines with different tuning options.