Split database test into separate read and write tests

[ottok]

The current database test runs both read and write operations. The title however says it tests "Queries per second". This is slightly misleading maybe?

I suggest you split it into read tests and title those results are "queries per second" and into write tests where the result is titled "operations per second" or simply just "read queries" and "write queries". Most of the time WordPress is doing read queries and it makes sense to compare pure read speeds. In particular in clustered environments the read speeds can be super high while write speeds are slower due to having to wait for multiple database servers to acknowledge the write.