Store AHWB in NN canonical memory type -- hal

Prior to this CL, the canonical memory type only held a SharedHandle,
which mirrors the behavior of native_handle_t/hidl_handle. This means
memory types including AHardwareBuffer were stored as this SharedHandle
type. With this CL, the canonical memory type is stored directly as
AHardwareBuffer to avoid using non-NDK AHardwareBuffer calls in the NN
runtime.

Bug: 179906132
Test: mma
Test: NeuralNetworksTest_static
Test: presubmit
Change-Id: I394071c193d15ac0c90ac47e5a2a9a79c635db6c