Fix texture corruption

When memory gets low on a device, activities flush everything they can.
Hardware-accelerated activites, such as Launcher, flush GL resources and destroy
the GL context. However, some resources were still hanging around, due to deferred
destruction policies (we don't delete layers until the DisplayLists they are in
are finalized, to ensure we don't deref deleted objects). This meant that we were
referring to obsolete GL data in these objects. in particular, it meant that we might
come around later, after a new GL context was created, and delete a texture object
that was incorrect. We use the layer's "texture id" to refer to the texture underlying the
layer. But if there's a new GL context, then this texture ID is no longer valid, and
we may be deleting the texture that a different object (layer, icon, whatever) is referring
to, because the driver may return that same ID under the new GL context.

The fix is to more aggressively delete things that we know will not be used again
when the GL context is destroyed. In particular, we delete all resources being used
by all DisplayLists at GL context destruction time.

Issue #7195815 Textures corruption on all devices, in many apps

Change-Id: I52d2d208173690dbb794a83402d38f14ea4c6c22