Helpers to generate random numbers, including simple Nim types
* disable C++ tests
* there are too many `const` vs `non-const` issues to run these tests -
C++ never actually worked
* add generateBytes to make fresh seqs
Co-authored-by: Mamy Ratsimbazafy <mamy_github@numforge.co>
Co-authored-by: Etan Kissling <etan@status.im>