DO NOT MERGE ANYWHERE Emulator: Enhance qemu_pipe.h to handle partial read and write

Partial read and write happen and it is better to try again
unless there is some hard error. This is meant to fix some
flaky behavior of emulator pipe services, hopefully.

BUG: 35207286

manually tested this on emulator image.

Change-Id: If033c815e621002313c45d1bcd9a92d2d75da4ad