Make a decision ABCI vs Rollkit to decide the current proposer

[S1nus]

This is underspecified and requires a final decision before we proceed. There are two options, the tradeoffs emerge in the form of how "key rotations" would be implemented.

1. Rollkit decides the proposer
Pro
We could very easily enforce centralized sequencers in Rollkit with minimal changes to the code. This would prevent user-error from ABCI app devs.
Con
No mechanism for sequencer key rotations. We'd need to add a feature for that in Rollkit, OR we do nothing and simply let the rollup devs handle sequencer key rotations via hard-forks, which might not be so bad for the vA release.

2. ABCI decides the proposer
Pro
Responsibility for sequencer key rotation feature is shifted from Rollkit up to the ABCI App
Con

• We would need to pay more attention to the cosmos-sdk to prevent user-error
• We would need to write a key rotations module in cosmos-sdk to replace the staking module.
• we don't currently have any cosmos-sdk code for this, nor do we have plans to develop and audit such a thing

[Manav-Aggarwal]

In favor of Rollkit deciding the proposer

[S1nus]

In favor of Rollkit deciding the proposer

PR in the works

[MSevey]

In favor of Rollkit deciding the proposer

Agreed, seems like the ABCI option has the same and more cons.

[S1nus]

related to:

#1272
#1273

(will be solved in the follow-up PRs to the linked issues)