Downgrade generated test harness for NDK libc++

NDK libc++ does not yet support full C++14. This CL replaced use of
std::get with type as well as auto lambda arguments with equivalent
C++11 constructs in the VTS test harness for NNAPI.

Test: VtsHalNeuralnetworksV1_0TargetTest
Bug: 63905942
Change-Id: If75e7c088e9221a70bcc47bc647e0dd7b045bfa1