onnxruntime

FP16 conv (#15062)

### Description

Convolution for fp16 datatype. Use NHWC for computation. For NCHW input,
it rearranges the input tensor to NHWC format before computing the
result.

Support two optional fusion:

1. Activation
2. Add (not yet implemented)

### Motivation and Context

Accelerating fp16 inference