PM: Get a random value between [min, max].

This is required for generating random values used for scattering. In
doing so, we shift to using an STL provided generator and distribution
function.

BUG=chromium:358323
TEST=Unit tests.

Change-Id: I6e758605f1d8123ab73a81906ecf7ad83c5e6cb9
Reviewed-on: https://chromium-review.googlesource.com/198780
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>