Add weak platform independent PRNG to test framework.

Implement the GNU C library's random(3) pseudorandom number generator.
The algorithm is described: https://www.mscs.dal.ca/~selinger/random/



The rationale is to make the tests repeatable across differing platforms with
different underlying implementations of the random(3) library call.

More specifically: when executing tests with random ordering.

[extended tests]

Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/9463)

(cherry picked from commit e9a5932d04f6b7dd25b39a8ff9dc162d64a78c22)