use Waku Network cluster id as default for autosharding

[adklempner]

This is a feature or change request

Problem

To setup a node for autosharding, a user needs to explicitly specify both content topics and a cluster id to determine the pubsub topics. According to the RFC, the Waku Network always uses a cluster id of 1.

Proposed Solutions

Modify any functions that accept sharding parameters to accept a list of content topics without a cluster id, in which case the default cluster id should be set.

Notes

[chair28980]

Internal dogfooding issue: #1812