Android SurfaceView shutdowns may be causing ANRs

[sjg-wdw]

We have a difficult (so far impossible) to reproduce bug that's resulting in a lot of stakeholder crashes.

The problem appears to be one GLSurfaceView shutting down while another is running.
This shouldn't be a problem, but there might be a set of really obscure cases where it takes a while for one to pass through the wait() logic if another one is rendering.

The change we'd like is to make the GLThreadManager in MapboxGLSurfaceView a local object. There's no apparent need for it to be global. In theory each surface view should be able to negotiate its own shutdown with its own objects and not need to coordinate with the others.

Yeah, in theory. So we'll want to test that pretty heavily. There's a mode in the Android test app that creates and destroys surface views as you scroll around. Try that for testing.