[EPIC] Implement `RelayerHelper` contract

[srdtrk]

Summary

Right now, the size of ICS26Router nearly exceeds the allowed limits. We can reduce the size of the contract by breaking some of its functionalities into a RelayerHelper contract while also improving the relayer experience.

This pattern would also allows us to implement callbacks and other convenience features such as multipass in a non-invasive and gas safe manner.

Problem Definition

The current size of ICS26Router makes it impossible to add new features to it, such as relayer whitelisting in #376. This is partially due to a lot of convenience functions and queries having been placed in ICS26Router.

Use cases

We can immediately move the following functions into the relayer helper:

• Multicall
• convinience queries such as:
  • isPacketReceived
  • isPacketReceiveSuccessful
  • queryPacketReceipt
  • queryPacketCommitment
  • queryAckCommitment
• Relayer whitelisting

We should also add the following items for better DX overall:

• Multipass (multicall without fully reverting the tx)
• Relayer gas limits and protections
• callbacks

---

For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged/assigned
• Estimate provided