[Python] Add a switch for truncating intraday milliseconds in Date64 in Python conversion

### Describe the enhancement requested

https://github.com/apache/arrow/blob/d09233af103bbfcd3617820192d78fff44d5c73e/python/pyarrow/src/arrow/python/python_to_arrow.cc#L312

This would also have to be done for https://github.com/apache/arrow/pull/48466 to be consistent.

### Component(s)

Python