Increase and improve random number generator tests

[ceolin]

Description

Random number generator (RNG) is a critical component of our system, used in various security functions, ranging from cryptographic key generation to entropy pooling. Ensuring the robustness and unpredictability of the RNG is crucial for maintaining system security and reliability.

Problem

Our current test suite for the RNG implementation does not adequately cover all edge cases and lacks checks against known RNG vulnerabilities (e.g., bias, predictability, and entropy source failures). This oversight could potentially expose the system to risks where the RNG might not meet the required cryptographic standards, especially under atypical conditions or stress.

Describe the solution you'd like

Would be nice to have something similar to diehard testsuite

The suite includes tests such as:

Birthday spacings Determines whether the differences between the sorted values of a sequence resemble the spacings between birthdays in a calendar year.
Overlapping permutations Examines the number of permutations of five consecutive integers in a sequence of random numbers.
Ranks of matrices Measures the rank of randomly generated binary matrices.
Random spheres Tests the distribution of a sequence of points randomly placed in a cube.

These tests are very thorough and are used to ensure that RNGs do not exhibit any detectable non-randomness, which is crucial for applications like cryptography, where the unpredictability of random numbers is fundamental to security.