Update D4PG to match DQN style.
Update D4PG to match DQN style.

- Single process agent hides reverb details.
- Work from separate dataclass config where possible.

PiperOrigin-RevId: 345319038
Change-Id: I9464c885067fe0d0b1462f82e94dbc4c66744dd9

deepmind/acme,deepmind/acme