Add time metadata to actors

In many cases it's useful to have some time metadata for actors (e.g. created / updated time). Today there are no fields to track this.

- `create_time`: Timestamp when actor is created. Immutable.
- `update_time`: Last time the actor was modified in any way (suspended, resumed, updated, etcCanc).
- `last_resume_time`: Timestamp of the most recent transition into RUNNING.
- `total_running_duration`: Cumulative time the actor spent running, since creation. Never resets. (this could be tricky to get right with high resolution if ate-apiservers have some clock skew)

The https://google.aip.dev/142 has some guidelines on how to deal with times in gRPC APIs. We should probably use the `google.protobuf.Timestamp` and `google.protobuf.Duration` well-known protos.