This was an attempt to move saturating_arithmetic.zig to the "passing
for stage2" section, which did not pan out due to the discovery of 2
prerequisite items that need to be done, but I did make a bug fix along
the way of the calculation of max/min integers.
This commit also simplifies the saturating arithmetic behavior tests to
depend on less of the zig language that is not related to saturating
arithmetic.
ac2333ee63