Implements a basic version of AndroidRuntime for host

This creates a simple implementation of AndroidRuntime that can be used
when running libandroid_runtime on host. It is automatically created and
run when the library is loaded through JNI.
This removes any specific code related to the way layoutlib is setup so
that this can be used and customized for different host running
environments.

Flag: NONE host-only change
Bug: 322360037
Test: load libandroid_runtime for host
Change-Id: I326d3d24a22437ad6df8d2e986087299d56c1d87