startop: Add iorap.stress.memory tool to test system with less RAM

iorap.stress.memory <optional:bytecount> will mlock that amount of RAM
with randomly-written values, ensuring we avoid kernel optimizations
such as swap, zram, ksm, etc.

Bug: 137397549
Test: iorap.stress.memory  # and visually inspect VmLck output.
Change-Id: Icf0786b2607a9a8bc7b6d77aa119abfc0249e7e0
2 files changed