Track and update tendermint changes in privval package

[liamsi]

• ping messages will go away with Refactoring Remote signers tendermint#3370
• amino prefixes change with: double check consistency with Improve Remote Signer implementation tendermint#3351

This issue is to track the changes there and update the KMS accordingly.

[tarcieri]

@liamsi do these need to happen prior to the prop 5 upgrade?

[liamsi]

So far only tendermint/tendermint#3351 was merged into the tendermint v0.31 releases (which will be used in the hub). The diff looked like the amino prefixes will change which is in fact not the case. I updated the description above.

The other change (tendermint/tendermint#3370) will make it into tenderment v0.32 and is not necessary for the prop 5 upgrade. @jleni and I want more testing and confidence that the refactoring does work as expected.

[tarcieri]

@jleni if there are tendermint-rs changes that still need to happen, can you open a new issue about this at:

https://github.com/interchainio/tendermint-rs

Otherwise closing this as the relevant code has been relocated to the above repo.