Adds float16 support for DEQUANTIZE/FLOOR/MEAN.

Bug: 118607842
Bug: 118608102
Bug: 118605898
Test: NeuralNetworksTest_static
Test: VtsHalNeuralnetworksV1_2TargetTest --hal_service_instance=android.hardware.neuralnetworks@1.2::IDevice/sample-all
Change-Id: I694816d92ac7b138c157b8d9648da32576a05fa2