Remove endian-sensitivity from Abseil's RNG

Remove endian-sensitivity from Abseil's RNG

Forwarded: yes
Applied-Upstream: https://github.com/abseil/abseil-cpp/commit/c36d825d9a5443f81d2656685ae021d6326da90c

Ensure that the Abseil random number generator produces identical output
on both big- and little-endian platforms by byte-swapping appropriately
on big-endian systems.

The author works at Google. Upstream applied this patch as Piper
revision 355635051 and exported it to GitHub; the Applied-Upstream URL
above points to the exported commit.

Gbp-Pq: Name endian-random.diff