Add a test Fibonacci extension

This is an example of a vendor extension.

This extension also includes a CPU driver implementation so that we can make
sure our extension handling code paths work.

Bug: 118606713
Test: NeuralNetworksTest_static --gtest_filter="*Extension*"
Change-Id: Ibe0fc5356baa909bce8424138bd5cfac9f74648f
8 files changed