Adds float16 support to generated tests.

Uses the _Float16 type (ISO/IEC TS 18661-3:2015) for storage.

Test: VtsHalNeuralnetworksV1_2TargetTest --hal_service_instance=android.hardware.neuralnetworks@1.2::IDevice/sample-all
Bug: 113563458
Change-Id: I1779b828d397b5354dc854c68d21c159cd5b582c
Merged-In: I1779b828d397b5354dc854c68d21c159cd5b582c
(cherry picked from commit efa4c814)