uint: replace hex with hex-simd

[Nugine]

Benchmark:

from_str                time:   [372.11 ns 373.23 ns 374.35 ns]                     
                        change: [-44.782% -44.174% -43.681%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 1 outliers among 100 measurements (1.00%)
  1 (1.00%) high mild