Merge "Upgrade pthreadpool to 344531b40881b1ee41508a9c70c8fbbef3bd6cad" am: 648365d11d am: 7b7f865f8e

Original change: https://android-review.googlesource.com/c/platform/external/pthreadpool/+/1520473

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I58f93853b625f5ebe5b111c246d42ca1e3f2cc83