arrow

ARROW-16898: [Python] Fix pandas conversion failure when using non-str index name (#13402)

Ticket: https://issues.apache.org/jira/browse/ARROW-16898 

When do `Table.from_pandas(df)`, current code didn't convert `index` name to str (it did [convert `column` name to str](https://github.com/apache/arrow/blob/apache-arrow-8.0.0/python/pyarrow/pandas_compat.py#L356)), so that it will fail if **non-str index name** in df.

Code to reproduce:
```python
import pandas as pd
import pyarrow as pa

df = pd.DataFrame({0: [1, 2, 3], 1: [4, 5, 6]})
df = df.set_index(0)
pa.Table.from_pandas(df)
```

Error:
```python
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Input In [3], in <module>
      4 df = pd.DataFrame({0: [1, 2, 3], 1: [4, 5, 6]})
      5 df = df.set_index(0)
----> 6 pa.Table.from_pandas(df)

File ~/src/mlpsandboxrt/venv/lib/python3.8/site-packages/pyarrow/table.pxi:1394, in pyarrow.lib.Table.from_pandas()

File ~/src/mlpsandboxrt/venv/lib/python3.8/site-packages/pyarrow/pandas_compat.py:610, in dataframe_to_arrays(df, schema, preserve_index, nthreads, columns, safe)
    608     for name, type_ in zip(all_names, types):
    609         name = name if name is not None else 'None'
--> 610         fields.append(pa.field(name, type_))
    611     schema = pa.schema(fields)
    613 pandas_metadata = construct_metadata(df, column_names, index_columns,
    614                                      index_descriptors, preserve_index,
    615                                      types)

File ~/src/mlpsandboxrt/venv/lib/python3.8/site-packages/pyarrow/types.pxi:1698, in pyarrow.lib.field()

File stringsource:15, in string.from_py.__pyx_convert_string_from_py_std__in_string()

TypeError: expected bytes, int found
```

This PR uses `_column_name_to_strings` to convert the index name to str before use it. 

Lead-authored-by: Martin Liu <martinliu@lyft.com>
Co-authored-by: Martin Liu <1459760+martin-liu@users.noreply.github.com>
Signed-off-by: David Li <li.davidm96@gmail.com>