Implement RenderThread for host

This creates a host implementation of RenderThread in libhwui.
In order to do this, it also implements ThreadBase, ReadBack,
CacheManager. Most of those implementations are no-op.

Bug: 322360037
Test: build libandroid_runtime on host
Change-Id: If72f46fe9baa645ff95330b971a102c2db554bb6
12 files changed