Adds benchmarks for insertion/operations/lookup

[xfbs]

This PR add benchmarks for insertion, operations and lookups. For now, I have only implemented them for the map types, my reasoning being that the set types are rather small wrappers around those and as such, measuring the performance of the map types should be sufficient.

The benchmarks are configurable using constants. You can set these to different values and observe how the code performs. The available constants are:

• Key: key types being used
• Value: value types being used
• COUNT: count for the insertions
• OPERATIONS: number of operations
• LOOKUPS: number of lookups

The benchmark is also set to calculate throughput, such as to have a better understanding of the the times mean. Note that the rangemap likely scales O(n log n), so that changing the insertions/operations/lookups affects the measured throughput (in other words, the throughput does not stay constant).

I have used proptest to generate the input sets here, simply because it is convenient.

[jeffparsons]

🚀