Fix bytes_to_scalar for float/complex on RISC-V

[XYenChi]

变更说明 / Summary

Fix bytes_to_scalar for float/complex on RISC-V

bytes_to_scalar previously round-tripped raw bytes through Python
float/complex values (via ctypes) before constructing the tensor. This
loses NaN bit patterns on architectures (such as RISC-V) that
canonicalize NaNs in floating-point loads/conversions, causing
test_bytes_to_scalar_cpu_{float32,float64,complex64,complex128} to
fail with mismatched storage bytes.

Construct the scalar tensor by reinterpreting the raw bytes as the
target dtype via tensor.view(dtype), so all input bit patterns
(including NaN payloads) are preserved exactly.

Test Plan:
python test/test_torch.py TestTorchDeviceTypeCPU.test_bytes_to_scalar_cpu_complex64

关联 Issue / Related issue

验证方式 / Validation

检查清单 / Checklist

• The change is focused and contains no unrelated modifications.
• I have followed the target repository's contribution guidelines.
• I have added or updated tests where applicable.
• I have updated related documentation where applicable.
• I have run the relevant formatting, lint, build, and test checks.
• I have described known limitations or compatibility impact.