[P2P] Integrate Raintree as Router in LibP2P Messaging

[jessicadaugherty]

Objective

Implement Raintree as a pubsub router in peer discovery for messaging.

Origin Document

Opportunity identified while integrating Pocket with LibP2P in #347

Goals

• improve the efficiency, scalability, and security of message dissemination

Deliverable

• Integrate (and refactor if required) Raintree with libp2p
• Modify LibP2P to use Raintree for direct message routing (don't handle streams directly, move a layer up and use pubsub for direct messaging)

Non-goals / Non-deliverables

• Refactoring addressbook

General issue deliverables

• Update the appropriate CHANGELOG(s)
• Update any relevant local/global README(s)
• Update relevant source code tree explanations
• Add or update any relevant or supporting mermaid diagrams

Testing Methodology

• All tests: make test_all
• LocalNet: verify a LocalNet is still functioning correctly by following the instructions at docs/development/README.md

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Creator: @jessicadaugherty