BUG: read_sql with dtype_backend="pyarrow" returns date/time as string (#56551)

[aboderinsamuel]

• closes BUG: read_sql() does not handle date nor time datatypes correctly when using pyarrow (but works for datetime) #56551
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With dtype_backend="pyarrow", read_sql returned datetime.date and datetime.time
columns as string[pyarrow] instead of date32/time64 (datetime columns were already
correct). These objects have no NumPy dtype, so the object-array conversion fell back to
string before pyarrow could infer the type. The fix re-infers such columns via pyarrow only
when the values are date/time; numeric, string, null, and decimal columns are unchanged.

Tested directly against _convert_arrays_to_dataframe because SQLite returns date/time as
text and cannot exercise the object-to-arrow conversion path.