Generate random matrices of fixed size and sparsity

[XeniaGabriela]

Write a function to generate a matrix of size n x m with

• a fixed number of zeros per row, randomly distributed
• randomly generated non zero values (sparsity)

[XeniaGabriela]

Implemented with commit https://github.com/Quant-X-Security-Coding-GmbH/svd-challenge/commit/e19b919040962ba51ad5a1376e01dfb02885014e