We should subscribe to data columns subnets when following the chain optimistically

When we are in optimistic sync mode:
i.e.:
```
Syncing     *** Slot: 13471644, Head slot: 13471643, Waiting for execution layer sync, Connected peers: 100
```

We don't subscribe to data column subnets. Which means we follow the chain by downloading columns via RPC.
This is particularly relevant when running node in full custody via `p2p-subscribe-all-custody-subnets-enable`.