Google Benchmark

[Kalashnikovni]

I've added Google Benchmark, which might be useful also for the partitioner, to the project with the following commands:

FetchContent_Declare(
  google_benchmark
  GIT_REPOSITORY https://github.com/google/benchmark.git
  GIT_TAG v1.6.1
)
FetchContent_MakeAvailable(google_benchmark)

If there is any better way to achieve this, please comment it @joaquinffernandez and @francosansone.