Start validators after ETH1 sync is done

[amirylm]

Is your feature request related to a problem? Please describe.

Validators starts to sync history while ETH1 sync is running, this is a wrong behavior as future events can deregister validators and therefore makes the history sync redundant.

Describe the solution you'd like

Validators shouldn't start before ETH1 sync is done.

Describe alternatives you've considered

Additional context