[RenderEngine] Move RenderEngine to libs/renderengine

To do side-by-side comparison between readback buffer from hardware composer
and client target of RenderEngine, we need RenderEngine to be accessible in
VTS, which means RenderEngine should be part of VNDK. This patch moves
RenderEngine out of SurfaceFlinger to libs/renderengine.

BUG: 112585051
Test: build, flash, boot and do some display validation
Change-Id: Ib6b302eaad04c7cc6c5bae39b1d25b38be188d01