[Serialization] Sync `_get_dtype_size` with safetensors (#4902)
Adds uint16/uint32/uint64, float8_e4m3fnuz, float8_e5m2fnuz,
float8_e8m0fnu, float4_e2m1fn_x2 and complex64 to the dtype size table.
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>