wasi_nn_tensorflowlite.cpp get_output seems to return the number of float32

[yamt]

glancing at the code, wasi_nn_tensorflowlite.cpp seems to return the number of fp32 values via output_tensor_size.
i believe it should return number of bytes.

well, at least for wasi_ephemeral_nn.
i'm not sure what should do for the legacy wamr-specific "wasi_nn" api.
it seems the size of tensor sizes has always been inconsistent for "wasi_nn". cf. #3223