Backport Tendermint v0.35.x to SDK v0.44 release branch

[ValarDragon]

Summary

On the SDK call today, we talked about backporting Tendermint v0.35.x into the SDK v0.44.x release line. (And maybe we need to tag this as SDK v0.45)

As shown in #10210 there is a lot of changes here. Doing this is mainly blocked on someone spending the time to produce the rebase. Should also backport PR that fixes #9962

Problem Definition

Prioritized mempool helps alot with TX fee issues. Further, the new p2p work is really helpful to be testing against to get more p2p issues solved on mainnets.

Proposal

Update SDK v0.44 branch to have Tendermint v0.35.

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For Admin Use

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[alexanderbez]

Wouldn't introducing TM v0.35 into SDK v0.44 technically be a breaking change? Specifically, there are numerous APIs in TM that changed or were removed outright and as a result things changed in the SDK to accommodate that.

[aaronc]

It would need to be 0.45. But we can still do that in a backport way if needed.

[tac0turtle]

Tendermint has a few changes that need to be implemented and taken into consideration. For ed25519 changes it is recommended to do a coordinated upgrade, otherwise there are edge cases that can cause problems. There was also a db key migration, users would need to migrate all keys in order to use 0.35 with 0.44. All in all, it is possible, but not recommended for live chains.

[ValarDragon]

Ah didn't realize there was a db migration needed

[robert-zaremba]

yeah, this is what we were talking during the last Friday: breaking changes can't go into 0.44.
The discussed alternative (0.45 only with new tendermint) might not be better. Mempool prioritization currently requires requires middleware work we did in master and that was also a substantial rework. IMHO it would be better to focus on releasing 0.45 earlier than latter and freezing features soon.

Let's close this issue and open a new one if needed.