Function test_pow_one_ulp_below_one_impl

tests/fl/math/fixed_point.cpp:5160–5167

// the snap, this must collapse to exactly one.
template <typename FP>
static void test_pow_one_ulp_below_one_impl() {
    const FP just_below = FP::from_raw(static_cast<raw_t<FP>>(FP::SCALE - 1));
    const FP one(1.0f);
    const FP gamma_2_8(2.8f);
    const FP gamma_3_2(3.2f);
    FL_CHECK_EQ(FP::pow(just_below, gamma_2_8).raw(), one.raw());
    FL_CHECK_EQ(FP::pow(just_below, gamma_3_2).raw(), one.raw());
}

// Same as above, two LSBs below 1.0 -- also inside the snap window.
template <typename FP>