migrate to pyproject.toml

[rinarakaki]

This is the tracking issue for googleapis's pyproject.toml support.

List

• [ ] https://github.com/googleapis/google-auth-library-python/pull/1607
• [x] https://github.com/googleapis/python-api-core/pull/736
• [ ] https://github.com/googleapis/python-cloud-core/pull/304
• [x] https://github.com/googleapis/google-cloud-python/pull/13550
• [x] https://github.com/googleapis/proto-plus-python/pull/496
• [ ] https://github.com/googleapis/google-resumable-media-python/pull/456
• [x] https://github.com/googleapis/google-cloud-python/pull/13551
• [ ] AI Platform https://github.com/googleapis/python-aiplatform/pull/4549
• [ ] Audit Log https://github.com/googleapis/python-audit-log/pull/153
• [x] BigQuery https://github.com/googleapis/python-bigquery/pull/2041
• [ ] DNS https://github.com/googleapis/python-dns/pull/290
• [ ] Logging https://github.com/googleapis/python-logging/pull/949
• [ ] Pub/Sub https://github.com/googleapis/python-pubsub/pull/1277
• [ ] Spanner https://github.com/googleapis/python-spanner/pull/1211
• [ ] Storage https://github.com/googleapis/python-storage/pull/1364

Closes #10528.