Add GraphicsEnv to libgui

This singleton class stores information provided by the framework and
makes it available to EGL/GLES/Vulkan loaders. It will eventually
replace vulkan::LoaderData and possibly the egl blob cache directory
storage.

Bug: 33531483
Test: various apps w/ and w/o driver package installed
Change-Id: If8b84fd38428f1cc9fcee8ffc25eb90cd87cedb4