Clean-up egl image preallocation

Allocate EGL images in onFrameAvailable, instead of a custom
onBuffersAllocated callback. This way we reduce traffic over binder
while still performing GL work ahead of time in queueBuffer().

Bug: 130567928
Test: systrace
Change-Id: I4070e9ddbd379dac3d809d0e7edb2855fc8b7a80