fix: crash for bigtable's scan_throughput_benchmark (#3905)
fix: crash for bigtable's scan_throughput_benchmark (#3905)

On Windows+CMake+Debug builds the C++ library has a few more assertions,
and it crashed when we passed invalid ranges to the random number
generators.
googleapis/google-cloud-cpp,googleapis/google-cloud-cpp,googleapis/google-cloud-cpp,googleapis/google-cloud-cpp