Features
- spanner/admin/database: adds PITR fields to backup and database (0959f27)
- spanner/spannertest: restructure column alteration implementation (#3616) (176400b)
- spanner/spansql: add complete set of array functions (#3633) (13d50b9)
- spanner/spansql: add complete set of string functions (#3625) (34027ad)
- spanner: add option for returning Spanner commit stats (c7ecf0f)
- spanner: add option for returning Spanner commit stats (7bdebad)
- spanner: support CommitStats (#3444) (b7c3ca6)