Features
- bigquery/connection: add cloud spanner connection support (458f15b)
- bigquery/storage/managedwriter/adapt: add schema -> proto support (#4375) (4ff6243)
- bigquery/storage/managedwriter: add append stream plumbing (#4452) (b085384)
- bigquery/storage/managedwriter: add base client (#4422) (4f7193b)
- bigquery/storage/managedwriter: add flow controller (#4404) (9dc78e0)
- bigquery/storage/managedwriter: add opencensus instrumentation (#4512) (73b6f5e)
- bigquery/storage/managedwriter: add state tracking (#4407) (4638e17)
- bigquery/storage/managedwriter: naming and doc improvements (#4508) (663c899)
- bigquery/storage/managedwriter: wire in flow controller (#4501) (40571fa)
- bigquery: add more dml statistics to query statistics (#4405) (99d5728)
- bigquery: support decimalTargetType prioritization (#4343) (95a27f7)
- bigquery: support multistatement transaction statistics in jobs (#4485) (4565eb7)