Autodiscover hints default config (unreleased) was done at the hints
level, while it only makes sense for certain configs builder (logs).

This change moves this logic to the `logs` builder and improves how
users can define default settings for logs, ie:

Enable hints but disable log retrieval by default:

```
filebeat.autodiscover:
  providers:
    - type: docker # or kubernetes
      hints.enabled: true
      hints.default_config.enabled: false
```

Only containers with the `co.elastic.logs/enabled: true` annotation
will be retrieved.

```
filebeat.autodiscover:
  providers:
    - type: kubernetes # or docker
      hints.enabled: true
      hints.default_config:
        type: container
        paths:
          - /var/log/containers/*${data.container.id}.log
```

Logs are read by default for all containers, using the given input
settings. Containers with `co.elastic.logs/enabled: false` annotation
will be ignored.