Inference gRPC/Rest client to support FP16

[yuzisun]

/kind feature

Describe the solution you'd like
Triton client supports FP16, kserve rest/grpc should also support transporting FP16.
https://github.com/kserve/kserve/blob/master/python/kserve/kserve/protocol/infer_type.py#L278-L296

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