Add support for Python 3.15

This bug tracks the remaining work to support 3.15

- [ ] Publish `google-crc32c` wheels which is blocking 3.15 support in these libraries (See related PR https://github.com/googleapis/python-crc32c/pull/254 to use the [Python limited C API ](https://docs.python.org/3/c-api/stable.html#limited-c-api)which could help unblock this ahead of the Python 3.15 formal release)
- [ ] google-cloud-bigtable
- [ ] google-cloud-storage
- [ ] 3.15 wheels for `pyarrow` https://github.com/apache/arrow/issues/50091 . Needed for
- [ ] bigframes
- [ ] db-dtypes
- [ ] google-cloud-bigquery
- [ ] google-cloud-bigquery-storage
- [ ] google-cloud-documentai-toolbox
- [ ] pandas-gbq
- [ ] sqlalchemy-bigquery
- [ ] 3.15 wheels for `pyproj` https://pypi.org/project/pyproj/#files . Needed for
- [ ] bigframes
- [ ] bigquery-magics
- [ ] google-cloud-bigquery
- [ ] pandas-gbq
- [ ] 3.15 wheels for `numba` https://github.com/numba/numba/issues/10581. Needed for
- [ ] google-cloud-documentai-toolbox
- [ ] 3.15 wheels for `lxml` https://pypi.org/project/lxml/#files. Needed for
- [ ] google-cloud-documentai-toolbox