abci's ValidatorUpdates is not compliant with SDK's ProtoMessage

[likhita-809]

Summary

Problem Definition

With current abci type's ValidatorUpdates, its not possible to migrate it to collections. We'll need a custom codec for it.

Proposal

Create a custom value codec for abci types ValidatorUpdates which is compliant with cosmos sdk's ProtoMessage.

[tac0turtle]

hmm could you point me to the code where this is the case

[likhita-809]

hmm could you point me to the code where this is the case

Here: https://github.com/cosmos/cosmos-sdk/blob/main/x/staking/keeper/keeper.go#L132
while migrating ValidatorUpdates to collections, the initial idea is to use collections.Item[abci.ValidatorUpdates] for defining ValidatorUpdates field in keeper struct. In this case, those protov2 API's are not compatible to encode using collections value codec.
But we can also use staking types's ValidatorUpdates for it which @testinginprod pointed out. He also made a PR to support protov2 APIs encoding for future use cases

Closing this as it is addressed in #17042