v0.46.0

• spanner:
  • Retry "Session not found" for read-only transactions.
  • Retry aborted PDMLs.
• spanner/spannertest:
  • Fix a bug that was causing 0X-prefixed number to be parsed incorrectly.
• storage:
  • Add HMACKeyOptions.
  • Remove *REGIONAL from StorageClass. MULTI_REGIONAL,
    DURABLE_REDUCED_AVAILABILITY, and REGIONAL are no longer StorageClasses but
    they are still LocationTypes.
• trace:
  • Remove cloud.google.com/go/trace. Package cloud.google.com/go/trace has been
    marked OBSOLETE for several years: it is now no longer provided. If you
    relied on this package, please vendor it or switch to using
    https://cloud.google.com/trace/docs/setup/go (which obsoleted it).