[OV EP] Consider whether we need precision config for OV NPU/CPU

[mingmingtasd]

Correct some details: With OV team's internal code library, it can support passing ACCURACY for all devices, but it seems only effective for GPU.

We can hard code to pass FP32, FP16 and ACCURACY to CPU/NPU/GPU to test:

1. CPU:
   FP16 or ACCURACY precision looks same as default FP32

2. NPU:
   FP32 or ACCURACY precision looks same as default FP16

In conclusion, precision config for OV NPU/CPU is not effective, NPU only supports FP16, CPU only supports FP32.

@huningxin