Batch log messages and downgrade log level

[potuz]

There are a few log messages that are very noisy

Messages proposed to batch:

• Sync committe messages should be batched by validator index.
• "Gossip message was ignored" should be batched by type/slot

Messages proposed to be downgraded

• "Set deadline for proposals and attestations"

Messages proposed to be removed:

• "Submitted sync committee messages succesfully to beacon node" when there aren't any validators in the sync committe and this message has "messages=0"

[terencechain]

@saolyn you might be interested in this