Explore switching from delayed agreement to immediate agreement

[rootulp]

Summary

Keynote Intro to ABCI ++ by Callum Waters describes that ABCI++ will support immediate agreement (also known as immediate execution).

Context

Currently celestia-core uses delayed agreement.

Proposal

Explore what the process is for switching from delayed agreement to immediate agreement. Some high level questions that come to mind:

1. Which release milestone (incentivized testnet, mainnet) do we want to include this feature in?
2. Can this switch be performed on a live network?
3. What are the pros / cons of switching?
   1. Pro: easier for developers to reason about
   2. Con: depending on when we adopt, immediate agreement is likely less battle tested than delayed agreement
4. Are there use cases enabled by immediate agreement that aren't possible with delayed agreement?
   1. Potentially fee burn

[evan-forbes]

As discussed, we cannot do fee burning or ISRs without immediate execution.

the biggest blocker of this is 100% in the cosmos-sdk, as we need to be confident that the rest of the sdk modules work fine in the context and there are no weird bugs.

this extremely likely to be an after mainnet things imo

[evan-forbes]

ref:
celestiaorg/celestia-app#49
#463