ASV: Add benchmarks for groupby with multiple categories

[rhshadrach]

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

Timings:

[ 78.57%] ··· groupby.MultipleCategories.time_groupby_extra_cat_nosort                 29.5±2ms
[ 82.14%] ··· groupby.MultipleCategories.time_groupby_extra_cat_sort                 54.4±0.1ms
[ 85.71%] ··· groupby.MultipleCategories.time_groupby_nosort                         23.0±0.2ms
[ 89.29%] ··· groupby.MultipleCategories.time_groupby_ordered_nosort                 23.3±0.1ms
[ 92.86%] ··· groupby.MultipleCategories.time_groupby_ordered_sort                   50.9±0.4ms
[ 96.43%] ··· groupby.MultipleCategories.time_groupby_sort                           50.4±0.3ms
[100.00%] ··· groupby.MultipleCategories.time_groupby_transform                       629±0.8μs

[mroeschke]

Thanks @rhshadrach