Improve performance of compare_dict_op

[alamb]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

#1330 introduced a significant cleanup for comparing dictionary arrays 🎉

However, it also may reduce performance as it indirectly calls value() repeatedly in an array which checks the bounds. This bounds check is necessary for known good dictionary arrays (where all the value entries are known to be valid indexes into the values array)

Describe the solution you'd like

As suggested by @viirya in #1330 (comment):

1. A benchmark showing the speed of comparing dictionary arrays
2. Implement something like unsafe take_iter_unchecked() that is used in compare_dict_op
3. Demonstrate that the benchmark is faster with the specialized approach

Additional context
All the context is on #1330