chore(bench): add const-hex to bench

[yjhmelody]

array_bytes::bytes2hex  time:   [144.29 µs 146.18 µs 149.05 µs]
                        change: [-1.3871% -0.3029% +0.7608%] (p = 0.61 > 0.05)
                        No change in performance detected.
Found 11 outliers among 100 measurements (11.00%)
  6 (6.00%) high mild
  5 (5.00%) high severe

hex::encode             time:   [149.35 µs 150.45 µs 151.82 µs]
                        change: [+0.4094% +1.3222% +2.2776%] (p = 0.01 < 0.05)
                        Change within noise threshold.
Found 14 outliers among 100 measurements (14.00%)
  10 (10.00%) high mild
  4 (4.00%) high severe

const_hex::encode       time:   [2.2628 µs 2.3300 µs 2.4055 µs]
                        change: [+1.2185% +5.2719% +9.5136%] (p = 0.01 < 0.05)
                        Performance has regressed.
Found 4 outliers among 100 measurements (4.00%)
  4 (4.00%) high mild

rustc_hex::to_hex       time:   [150.38 µs 151.80 µs 153.60 µs]
                        change: [+0.4301% +1.3696% +2.3517%] (p = 0.00 < 0.05)
                        Change within noise threshold.
Found 11 outliers among 100 measurements (11.00%)
  9 (9.00%) high mild
  2 (2.00%) high severe

faster_hex::hex_string  time:   [17.824 µs 17.926 µs 18.044 µs]
                        change: [-2.4599% -1.4254% -0.4763%] (p = 0.01 < 0.05)
                        Change within noise threshold.
Found 9 outliers among 100 measurements (9.00%)
  4 (4.00%) high mild
  5 (5.00%) high severe

faster_hex::hex_encode_fallback
                        time:   [17.770 µs 17.845 µs 17.932 µs]
                        change: [-5.5325% -4.6448% -3.8199%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 6 outliers among 100 measurements (6.00%)
  4 (4.00%) high mild
  2 (2.00%) high severe

array_bytes::hex2bytes  time:   [121.79 µs 122.94 µs 124.44 µs]
                        change: [-8.1342% -5.9473% -3.9038%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
  3 (3.00%) high mild
  5 (5.00%) high severe

array_bytes::hex2bytes_unchecked
                        time:   [104.80 µs 106.83 µs 109.45 µs]
                        change: [-8.1132% -5.2278% -2.7215%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 13 outliers among 100 measurements (13.00%)
  9 (9.00%) high mild
  4 (4.00%) high severe

array_bytes::hex2slice  time:   [109.99 µs 110.61 µs 111.35 µs]
                        change: [-16.566% -12.715% -8.9614%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 13 outliers among 100 measurements (13.00%)
  4 (4.00%) high mild
  9 (9.00%) high severe

array_bytes::hex2slice_unchecked
                        time:   [106.36 µs 107.01 µs 107.73 µs]
                        change: [+0.1300% +0.8262% +1.5455%] (p = 0.02 < 0.05)
                        Change within noise threshold.
Found 15 outliers among 100 measurements (15.00%)
  13 (13.00%) high mild
  2 (2.00%) high severe

const_hex::decode       time:   [22.506 µs 22.620 µs 22.746 µs]
                        change: [-0.9531% -0.1817% +0.5044%] (p = 0.64 > 0.05)
                        No change in performance detected.
Found 10 outliers among 100 measurements (10.00%)
  5 (5.00%) high mild
  5 (5.00%) high severe

hex::decode             time:   [158.77 µs 159.75 µs 160.91 µs]
                        change: [-4.1689% -1.5886% +0.2738%] (p = 0.20 > 0.05)
                        No change in performance detected.
Found 7 outliers among 100 measurements (7.00%)
  2 (2.00%) high mild
  5 (5.00%) high severe

hex::decode_to_slice    time:   [92.014 µs 92.959 µs 93.992 µs]
                        change: [-5.6023% -3.8389% -2.1713%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
  3 (3.00%) high mild
  5 (5.00%) high severe

rustc_hex::from_hex     time:   [164.63 µs 165.58 µs 166.69 µs]
                        change: [-2.6146% -1.9408% -1.2730%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 15 outliers among 100 measurements (15.00%)
  1 (1.00%) low mild
  5 (5.00%) high mild
  9 (9.00%) high severe

faster_hex::hex_decode  time:   [38.787 µs 39.093 µs 39.486 µs]
                        change: [-1.5174% -0.1346% +1.0835%] (p = 0.85 > 0.05)
                        No change in performance detected.
Found 6 outliers among 100 measurements (6.00%)
  3 (3.00%) high mild
  3 (3.00%) high severe

faster_hex::hex_decode_unchecked
                        time:   [16.099 µs 16.178 µs 16.267 µs]
                        change: [-0.7121% -0.0005% +0.6746%] (p = 1.00 > 0.05)
                        No change in performance detected.
Found 13 outliers among 100 measurements (13.00%)
  4 (4.00%) high mild
  9 (9.00%) high severe

faster_hex::hex_decode_fallback
                        time:   [16.057 µs 16.154 µs 16.269 µs]
                        change: [-0.6458% -0.0882% +0.4780%] (p = 0.75 > 0.05)
                        No change in performance detected.
Found 15 outliers among 100 measurements (15.00%)
  1 (1.00%) low mild
  4 (4.00%) high mild
  10 (10.00%) high severe