feat: optimize Filter Ping towards peers

[chaitanyaprem]

Background

As part of #1048 , moving Filter subscription management to go-waku and multiplexing channels towards users is being accomplished. But if there are multiple susbcriptions towards a peer, it can lead to multiple Filter ping requests every 5 seconds which is not optimal and doesn't scale.

Need to optimize the same so that a single Filter Ping is sent towards a peer.

Details

This kind of logic can be moved to peer-Manager along with maintaining healthy connections towards Filter-Peers(TBD: analyze)

Acceptance criteria

Unit tests to validate Filter pings based on different subscriptions towards a single peer.