EPIC: Include a relayer implementation

[srdtrk]

Description

Include a relayer implementation in this repo between Ethereum and Cosmos. This relayer implementation is intended to be used by service providers and/or frontends, as such, it will be built primarily as an RPC server, to which relayer users submit tx hashes which emit packets to be relayed.

Requirements

• Supports relaying Cosmos -> Ethereum via solidity-ibc-eureka and sp1-ics07-tendermint
• Supports relaying Ethereum -> Cosmos via the 08-wasm client we use.
• Runs as an RPC server which can receive concurrent requests.
• Supports batching via tx hashes.

Automated e2e tests

• Include a relayer test suite which tests the relayer. Not to replace manual relaying with the relayer in the main test suite.

QA scenarios

• Relaying a single packet
• Relaying multiple packets
• Usage via an external team

Tasks

• Create a relayer RPC server that only returns the chain info #122
• Add relaying capabilities from Cosmos to Ethereum and test it with 1 tx hash #127
• Add more relayer tests with multiple tx hashes and acknowledgements #136
• Add timeout tests to relayer #140
• Add Ethereum to Cosmos relayer module #152
• Relay 1 Recv packet from Ethereum to Cosmos
• Add tests for batch tx and ack relaying from eth to Cosmos
• Add timeout tests for relaying from eth to Cosmos
• Add a Cosmos to Cosmos relayer module with only with chain info #153
• Relay 1 RecvPacket from Cosmos to Cosmos #174
• Add tests for batch tx and ack relaying from Cosmos to Cosmos #179
• Add timeout tests for relaying from Cosmos to Cosmos #181

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For Admin Use

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• Appropriate labels applied
• Appropriate contributors tagged/assigned