random: Change testing random generator

The old random timer test was not random-looking
enough on some platforms.

Replace with new test which is psuedo-xoshiro.

The generator is still deterministic
and does not depend on entropy at all,
but should look more random for testing.

Change name of generator tree-wide also.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>