Make sure interop path works with draw_fn

plat_support to pass through the GL functor even if hwui is using vulkan
pipeline, since interop calls the GL functor.

Also remove sGLDrawThread and call functor on render thread, since
onDestroy and onContextDestroy are currently hard coded to run on render
thread as well, and functor expects all calls to be called on a single
thread.

Bug: 115613038
Test: draw_fn functor works with vulkan enabled
Change-Id: Ie3fa643695e95a6cc383f7ffe3eb3ad741792707