algo: Add pseudo-random test case for InsSort.
algo: Add missing break in for loop of InsSort. Between ~78% and ~97% faster.

benchmark                  old ns/op    new ns/op    delta
BenchmarkInsSort1e2Rand        34226         7268  -78.76%
BenchmarkInsSort1e3Rand      3047274       187338  -93.85%
BenchmarkInsSort1e4Rand    300289208      6540423  -97.82%