feat: provide content topic health for filter/lightpush

[igor-sirotin]

Problem

In Relay mode, there is TopicHealth provided that Waku clients can use to trigger discovery of more peers for give PusbsubTopic.

Would be nice to have a similar thing for light client (filter/lightpush).

In status-go (and I guess other Waku clients), we need to know when to discover more peers. In case of Relay this is per pubsub topic. In case of filter/lightpush this should be different (could be per content topic).

We need something that will tell is "hey, you better find some more peers".

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Ref:

• feat: connection health should be shard specific status-im/status-go#4628
• https://discord.com/channels/1110799176264056863/1414975481438011392/1428699392801636363