feat(rln-relay): Manage reconnections to the eth node

[rymnc]

Problem

When a wakunode running waku-rln-relay gets disconnected from the eth node, there is no attempt to reconnect to it, and therefore, will count every new message as invalid since it cannot receive updates to the membership group, and thereby cannot update its local merkle tree.

Suggested solution

After #1266 has been addressed, reconnection to the eth node must be handled, and events should be fetched from the last processed block.

Alternatives considered

Additional context

Acceptance criteria

• Reconnection to the eth node
• Resubscription to membership altering events with the last processed block

[rymnc]

Addressed in #1465. Will close upon its merge