random: deprecate `XOROSHIRO_RANDOM_GENERATOR`

Deprecate the xoroshiro128+ PRNG algorithm in favour of xoshiro128++.
xoshiro128++ is a drop-in replacement which is invisible from the user
perspective.

xoroshiro128+ is unsuitable because it is explicitly a floating-point
PRNG, not a general-purpose PRNG. This means that the lower 4 bits of
the output are actually linear, not random (from the designers,
https://prng.di.unimi.it/

). This means 1/8th of the generated data is
not random.

Additionally, xoroshiro128+ is not a 32bit algorithm, it operates on
64bit numbers. For the vast majority of Zephyr devices, this makes the
PRNG slower than it needs to be. The replacement (xoshiro128++) is
32bit, with no loss in state space (still 128 bit).

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>