Specialize Dict's key to ByteArray

  Looking at Aiken's repositories in the wild, no one is using Dict with
  anything else than ByteArray as key. The extra complexity we bring
  just for making it generic in the key argument seems not worth it.

  Plus, if we know the key is a ByteArray, we can perform some
  optimizations on a few functions looking for keys to short-circuit
  them instead of traversing a list entirely.

  Here's a comparison of the mem and cpu cost before and after the
  chance for a few tests (omitted tests have identical cost).

  | mem     | cpu     | bench                     |
  | ---     | ---     | ---                       |
  | -10.15% | -5.88%  | delete_3                  |
  | -4.00%  | -9.68%  | delete_4                  |
  | -3.80%  | -9.39%  | delete_5                  |
  | -31.03% | -42.88% | delete_6                  |
  | -15.26% | -26.34% | find_4                    |
  | -11.10% | -18.85% | from_list_2               |
  | -8.02%  | -16.26% | from_list_3               |
  | -12.15% | -25.39% | from_list_4               |
  | -19.24% | -36.11% | bench_from_list           |
  | -17.79% | -18.91% | bench_from_ascending_list |
  | -4.91%  | -10.58% | get_2                     |
  | -9.49%  | -14.63% | get_3                     |
  | -29.94% | -42.75% | get_4                     |
  | -23.66% | -37.70% | get_5                     |
  | -7.94%  | -5.03%  | has_key_3                 |
  | -9.97%  | -18.50% | has_key_4                 |
  | -16.46% | -23.61% | insert_1                  |
  | -16.52% | -26.24% | insert_2                  |
  | -13.82% | -22.08% | insert_with_1             |
  | -18.77% | -29.88% | insert_with_2             |
  | -19.12% | -30.52% | insert_with_3             |
  | -10.47% | -17.40% | keys_2                    |
  | 4.25%   | 5.06%   | map_1                     |
  | 2.94%   | 3.31%   | map_2                     |
  | -10.99% | -19.83% | size_3                    |
  | -7.94%  | -16.17% | union_1                   |
  | -17.74% | -28.17% | union_3                   |
  | -16.96% | -26.55% | union_4                   |
  | -15.91% | -25.10% | union_with_1              |
  | -10.47% | -17.39% | values_2                  |

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## UNRELEASED
+
+### Changed
+
+- Specialized all `Dict`'s key as `ByteArray`, and thus remove the need for passing an extra `bytearray.compare`.
+
 ## v1.7.0 - 2023-11-07
 
 ### Added