[mojo] Delete RemoteMessagePipeBootstrap

RemoteMessagePipeBootstrap is racy since it has no FIFO relationship
with mojo::edk::NodeController. Since there are no more callers of
mojo::edk::CreateMessagePipe(), we can simply remove that class and
always use mojo::edk::Create{Parent,Child}MessagePipe() instead, which
does not suffer from the race.

This is a cherry-pick of
https://crrev.com/8e3c814a822afe01b3893d48cb0dd7cb4e132b74

Bug: 33453258
Test: Android-on-Chrome OS still starts
Change-Id: I5967380d6075276b5cc20df3b599a013fea7067b
8 files changed