Benchmark critical paths in the driver (sending queries and receiving results)

[wprzytula]

Let's write benchmarks for critical operations of the driver, to be aware of how fast we are and to gauge impact of further optimisations
/ detect regressions.

Proposed functionality to be benchmarked:

• INSERTs with and without data,
• SELECTs with little and a lot of data,
• both prepared and unprepared statements,
• batches,
• paging
• concurrent executions API,
• TODO - more ideas welcome.

[adespawn]

It would be nice if benchmark would automatically compare state on two branches and generate reports from that.

[adespawn]

Currently we have benchmarks for (only in prepared version):

• Insert with data (including concurrent version)
• Select with little data (including concurrent version)

There are open PRs for following benchmarks:

• Batch Batch benchmark #218
• Select with a lot of data Benchmark deserialization #198