[Feature Request]: Add support for BigQuery structs in BigQueryIO with BEAM_ROW output type

### What would you like to happen?

The BigQuery to Python type conversion in [bigquery_schema_tools.py](https://github.com/apache/beam/blob/master/sdks/python/apache_beam/io/gcp/bigquery_schema_tools.py) currently only support primitive types. I would like to contribute by adding support for `REPEATED RECORD` fields. Since I am new to this project I would be thankful for some support in this.

@svetakvsundhar can you help me understand if the following can be achieved:

- change the logic in https://github.com/apache/beam/blob/5223ab466e78f403680a22036d3a769897d0cf9d/sdks/python/apache_beam/io/gcp/bigquery_schema_tools.py#L56 to
```python
for i in range(len(the_schema['fields'])):
if the_schema['fields'][i]['type'] in BIG_QUERY_TO_PYTHON_TYPES:
typ = bq_field_to_type(
the_schema['fields'][i]['type'], the_schema['fields'][i]['mode'])
elif the_schema['fields'][i]['type'] == "RECORD":
typ = generate_user_type_from_bq_schema(the_schema['fields'[i])
else:
raise ValueError(
f"Encountered "
f"an unsupported type: {the_schema['fields'][i]['type']!r}")
```
- add support for nested records in https://github.com/apache/beam/blob/5223ab466e78f403680a22036d3a769897d0cf9d/sdks/python/apache_beam/typehints/schemas.py#L513 since it is called in https://github.com/apache/beam/blob/5223ab466e78f403680a22036d3a769897d0cf9d/sdks/python/apache_beam/io/gcp/bigquery_schema_tools.py#L81

I think a similar feature request was implemented in the BigQuery->Avro->Beam conversion for the java sdk: [Pull request 9089](https://github.com/apache/beam/pull/9089).

### Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

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