[C++][Python] Unifying differing dictionaries in Arrow compute

### Describe the bug, including details regarding any error messages, version, and platform.

I received the above error when trying to run group_by() with a key column defined as dictionary

Also tried dictionary but received the same error.

When I changed the key column to string(), group_by() ran successfully.

I am therefore guessing that key columns of datatype dictionary are currently not supported by group_by().

Is group_by() support for dictionary key columns planned?

Current setup is :

Windows 11
Python 3.10
pyarrow 10.0.1

### Component(s)

Python

Start by reproducing group_by() with a dictionary key column using the reported Windows 11, Python 3.10, and pyarrow 10.0.1 setup, then trace the Arrow compute group_by path for dictionary handling. Done means dictionary key columns, including differing ordered states, are supported without the reported error and the behavior is covered by relevant tests.

Scritto dal modello di indicizzazione a partire dal testo della issue.